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Reproductive · Pregnancy
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In one pass If you want a child, the most valuable preparation happens in the 3 months before you conceive, not after.
Educational content, not medical advice — consult a clinician.
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Chapter 1
What to do before conceiving
If you want a child, the most valuable preparation happens in the 3 months before you conceive, not after. The baby's brain and spinal cord start to take shape in the first weeks, before you even know you are pregnant.
How early is that? The brain and spinal cord begin as a flat plate on the embryo's back. In the third to fourth week after fertilization, its two sides roll up and close from the middle toward both ends, like a zipper being pulled shut. Those few days fall right in the window when a period is only a few days late and no one has bought a pregnancy test yet, so folate has to be in your blood before then.
Preparing for pregnancy often gets drowned out by marketing for pregnancy milk powder, gummies and hyaluronic-acid drinks. What pre-conception guidelines around the world keep repeating is three things: get enough folate, bring your weight into a healthy range, and have both partners stop smoking and cut back on alcohol. Doing these three first is worth more than adding a pile of supplements after you are pregnant.
Two emergencies are worth knowing in advance. One-sided abdominal pain, vaginal bleeding, shoulder pain or fainting after a missed period may be an ectopic pregnancy. Sudden, severe, persistent pelvic pain with vomiting may be a twisted ovary (ovarian torsion). Both need the emergency department right away.
How early is that? The brain and spinal cord begin as a flat plate on the embryo's back. In the third to fourth week after fertilization, its two sides roll up and close from the middle toward both ends, like a zipper being pulled shut. Those few days fall right in the window when a period is only a few days late and no one has bought a pregnancy test yet, so folate has to be in your blood before then.
Preparing for pregnancy often gets drowned out by marketing for pregnancy milk powder, gummies and hyaluronic-acid drinks. What pre-conception guidelines around the world keep repeating is three things: get enough folate, bring your weight into a healthy range, and have both partners stop smoking and cut back on alcohol. Doing these three first is worth more than adding a pile of supplements after you are pregnant.
Two emergencies are worth knowing in advance. One-sided abdominal pain, vaginal bleeding, shoulder pain or fainting after a missed period may be an ectopic pregnancy. Sudden, severe, persistent pelvic pain with vomiting may be a twisted ovary (ovarian torsion). Both need the emergency department right away.
In practice · Three things to do before conceiving
1. Women take 400–800 μg of folate a day, starting 3 months before conception and continuing to week 12 of pregnancy. It is the best-supported single step against neural-tube defects, in which the tube that becomes the brain and spinal cord fails to close. In women who had already had an affected pregnancy, a randomized trial found a 72% lower risk of it happening again (MRC 1991). Women with a previous neural-tube defect, women on antiepileptic drugs, and women with diabetes may need a higher dose, but that is a doctor's prescription, not something to raise on your own. The UK NICE 2025 guideline states that a higher body weight on its own is not a reason to raise the dose.2. Bring your weight into a healthy range, which under the Chinese standard means a body mass index (, weight divided by height squared) of 18.5–23.9. Carrying too much weight raises the risk of gestational diabetes, preeclampsia, a very large baby and a cesarean birth, by roughly 2–4 times in observational studies. Being too thin makes preterm birth, low birth weight and a baby who does not grow enough more common. The man's diet matters too: a systematic review of observational studies (Salas-Huetos 2017) found that men who ate more fish, poultry, cereals, vegetables and fruit had better semen measures, and men who had more processed meat, alcohol and sugary drinks had worse ones. These are associations; no trial has shown that these foods cause the difference.
3. Stop smoking and cut back on alcohol, both partners. Any amount of alcohol in pregnancy can harm the baby (fetal alcohol spectrum disorder), and both WHO and the American Academy of Pediatrics say there is no safe amount to drink in pregnancy. The man's drinking is also linked with poorer semen quality, so the safest plan is for both partners to stop before conception. Smoking reduces blood flow to the placenta and raises the risk of low birth weight and sudden infant death.
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Clinical · Pre-pregnancy tests and chronic disease
Beyond those three, two things need one visit to a clinic. The first is a pre-pregnancy blood panel: anemia, thyroid, vitamins D and B12, rubella and chickenpox antibodies, and infections such as hepatitis B, plus a check of the gums. Whatever is short gets fixed before you try. The second is getting any chronic disease stable before you conceive: blood glucose, blood pressure, thyroid, and any antidepressant or anti-anxiety medicine you already take, which you should not stop on your own. Some blood-pressure drugs cannot be used in pregnancy and need to be switched by a doctor in advance. Which tests to run, and which numbers count as good enough, belong to your obstetrician; you do not need to memorize them.Evidence · Which pre-pregnancy supplements hold up
Pre-conception supplements are a heavily commercialized market. Sorting them by the type of evidence behind them makes the picture much clearer.The few backed by randomized trials or major guidelines:
Folate, 400–800 μg: prevents neural-tube defects. The support comes from several randomized trials and national guidelines, and the certainty is high.Vitamin D: the US recommended intake in pregnancy is 600 a day. In women who start out deficient, trials of supplementation lean toward better birth weight, but most are small and the conclusion is not settled.Iodine: WHO's figures are an intake of 150 μg a day for adults and 250 μg in pregnancy. That is the total from food, iodized salt and supplements, not a supplement dose. Iodine deficiency is one of the most common preventable causes of brain damage. Even so, according to the summary by the US NIH Office of Dietary Supplements, two randomized trials that gave iodine from early pregnancy to delivery found no difference in the children's cognitive, language or motor scores at one to two years.Treating iron-deficiency anemia: take iron when hemoglobin in pregnancy is below 110 g/L. Vitamin C taken at the same time helps the body absorb non-heme iron (the Hallberg 1989 review; WHO's 2016 antenatal care recommendations).
Inconsistent evidence, or useful only in specific groups:
Coenzyme (CoQ10): often sold as improving egg quality in women over 35 and sperm energy in men. But the most-cited study, Bentov 2014, was a small randomized trial in IVF patients that was stopped early, with fewer than half the planned participants finishing. It found no significant difference in egg chromosome errors or in clinical pregnancy rates. It is not a first choice, and it cannot be called effective.Inositol (myo-inositol and D-chiro): the 2023 international guideline on polycystic ovary syndrome (; Teede 2023) says it could be considered for metabolic measures, with limited clinical benefit, and treats its use for infertility (to help ovulation) as experimental. In women without PCOS, no benefit has been shown.Omega-3 ( and ): about 200 mg of DHA a day in pregnancy is the target several bodies give (the reasons are in the later chapter on DHA and the baby's brain). The evidence for starting before conception is weaker, though the direction is reasonable.
The majority, with weak or no evidence:
Pregnancy milk powder: mostly ordinary milk powder with DHA and folate added. If your diet is balanced and you already take folate and calcium separately, it adds nothing you need.Royal jelly and bird's nest: no randomized trials support them. Royal jelly has case reports of severe allergic reactions, including deaths; how often this happens cannot be estimated.Placenta extracts and deer-fetus paste: no randomized trials, and their ingredients and hormone content are often unclear.Male "fertility" blends (arginine, maca, yohimbine): the sperm improvement from maca comes only from small trials and is modest. Quitting smoking, cutting back on alcohol and losing excess weight come first.
Both partners starting half a year ahead with exercise, a better diet, quitting smoking, reaching a healthy weight and treating gum disease: these basics belong ahead of every supplement. The earlier and more basic the step, the more it is worth doing first.
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Mechanism · Eggs from the womb to menopause
Eggs and sperm follow opposite paths. While a girl is still in her mother's womb, her eggs are all made at once; after birth their number only falls, and it can never be topped up.The full timeline:
The peak is at week 20 of fetal life: the ovaries hold about 6–7 million primary oocytes, the most there will ever be. From then on the count only falls. Most are lost quietly while resting, a process called atresia, which continues throughout lifeAt birth, 1–2 million remain (80–90% already lost to atresia)At puberty (the first period), 300–500 thousand remain, and cyclic use beginsIn the reproductive years (12–45), each menstrual cycle recruits 15–20 follicles into a growing group. Usually only one ovulates (the dominant follicle) and the other 14–19 are lost. That small group is only the visible part: going from 300–500 thousand at puberty to fewer than 1,000 at menopause means roughly a thousand follicles are used up each month, almost all of them lost quietly from the resting pool. Over 30 years, that adds up to about 400–500 ovulationsAfter 35, the decline speeds up clearly, and the share of eggs with the wrong number of chromosomes (aneuploidy) starts to riseAround 40, few remain, and aneuploidy is about 50% (about 10% at 30), and the risks of miscarriage and Down syndrome both riseAt menopause (median age 51), fewer than 1,000 remain, which is functional exhaustion. Follicle-stimulating hormone () surges and (E2) drops sharply, bringing on perimenopausal symptoms
What this curve tells us:
1. Eggs cannot regenerate. A man's testes hold spermatogonial stem cells that keep dividing for life, so sperm are made continuously. A woman's ovaries have no such reserve of stem cells: each egg used is one gone. Ovarian age is not exactly the same as calendar age, but on average the two track each other closely.
2. An egg is not asleep; it is a cell division paused halfway. Before birth, each egg begins the special division that makes eggs (meiosis) and stops early in the first division, like a video frozen on one frame, for decades. Each month, the egg woken before ovulation finishes the first division, then stops again partway through the second. The second division is completed only at fertilization. During those decades of waiting the egg is exposed to damage and slowly collects errors, which is one of the main explanations for why eggs make more chromosome-count errors with age.
3. Anti-Müllerian hormone (AMH) reflects ovarian reserve. It is made by the granulosa cells of preantral and small antral follicles, so it shows how big the reserve still is. Unlike FSH, AMH changes little across the menstrual cycle and can be tested on any day. A common reading: at ages 20–30, below 1.0 ng/mL suggests low reserve; 1.0–3.5 ng/mL is a common range; above 3.5 ng/mL is often seen in polycystic ovary syndrome (). But these cut-offs shift with age and with the lab method, so go by the reference range printed on your report. The 2023 international PCOS guideline (Teede 2023) allows AMH only as a substitute for the ultrasound criterion in adults; it cannot diagnose PCOS on its own. More important still, AMH does not predict the chance of natural conception. What it predicts is how many eggs IVF stimulation is likely to yield.
4. Egg quality matters more than egg count. After 35, the main problem is rarely no eggs left; it is that a high share of the remaining eggs are aneuploid. The measures often promoted to improve egg quality mostly have weak evidence:
: the most-cited study, Bentov 2014, was a small randomized trial in IVF patients that stopped early and found no significant difference in egg chromosome errorsDehydroepiandrosterone (DHEA): a hormone, used only at some fertility centers, by doctors, in older patients or those with diminished ovarian reserve (DOR). Its benefit is disputed; do not take it on your ownInositol: relevant only to PCOS, and its use to help ovulation is still experimental (Teede 2023)Enough vitamin DLess alcohol, no smoking, weight loss, and a Mediterranean-style diet
None of these has been shown in trials to lower the rate of chromosome errors in eggs.
5. Egg freezing, in numbers:
Freeze 15–20 eggs before 35: the estimated chance of at least one baby eventually is about 70–90%Freeze 15–20 at 38: about 50–60%Freeze at 40 or later: about 30–40%, and freezing more eggs helps only a littleSince the 2010s, vitrification (flash-freezing) gives egg survival after thawing of 90% or more, so survival is no longer the bottleneck
These probabilities come from models built on age and egg number, and centers differ a lot. The point is that age sets egg quality; no number of frozen eggs buys back age.
"Ovarian maintenance" claims do not hold up:
Ovary massage has no evidence base, and some techniques may damage tissueBeauty-salon ovarian care is a commercial gimmick with no medical evidencePlacenta extracts, royal jelly and herbal tonics mostly do nothing, and some have undisclosed ingredientsWhat actually helps: no smoking, less alcohol, weight loss (in PCOS), treating chronic disease, enough sleep, and less chemical exposure (bisphenol A, phthalates)
Clinical red flags to take seriously:
Acute pelvic pain that is severe and persistent, with vomiting or fainting, may be ovarian torsion — get medical care immediatelyEctopic pregnancy: after a missed period, one-sided abdominal pain, vaginal bleeding, shoulder-tip pain or fainting — also get medical care immediately; it is one of the avoidable causes of death in women of reproductive age
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Mechanism · How sperm are made, and normal values
The sperm story runs opposite to the egg story. The testes are a factory that never shuts down, making new sperm throughout life, but the quality and output of the line slip quietly with age.How sperm are made:
The innermost ring of the testes' sperm-producing tubules holds stem cells that keep dividing for life (spermatogonial stem cells). A sperm cell starts from one of them and goes through a whole assembly line: type A spermatogonium → type B spermatogonium → primary spermatocyte → first meiotic division → secondary spermatocyte → second meiotic division → spermatid → sperm.
That line takes about 74 days. The sperm then spend about 12 more days in the epididymis, where they learn to swim and gain the ability to fertilize an egg. Altogether that is about 90 days, or 3 months. That is why lifestyle changes before conception need a 3-month head start to show up in the sperm.
Lower reference limits for semen analysis (WHO manual, 5th edition, 2010; the 6th edition in 2021 made small adjustments):
| Parameter | Lower reference limit |
|---|---|
| Semen volume | ≥ 1.5 mL |
| Total sperm count | ≥ 39 × 10⁶ per ejaculate |
| Sperm concentration | ≥ 15 × 10⁶/mL |
| Total motility (progressive plus non-progressive) | ≥ 40% |
| Progressive motility | ≥ 32% |
| Normal morphology | ≥ 4% (strict Kruger criteria) |
| Vitality | ≥ 58% |
| pH | 7.2–8.0 |
In the table, progressive motility means sperm swimming forward; non-progressive means moving in place or circling. A few points:
Normal is not optimal: a man whose results barely clear the limits can still have trouble conceiving naturallyNormal morphology of 4% sounds low because the stricter Kruger criteria were adopted after 1999; most fertile men actually sit around this levelSemen results vary a lot from sample to sample and depend on how the sample was collected. Do at least 2 tests, 2–4 weeks apart, and read them together
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Evidence · What drags sperm quality down
Sperm counts are falling (two meta-regressions by Levine's group; the 1973–2018 figures below come from the second, published online in 2022 and in print in 2023, so you will see it cited under either year):In men not selected for fertility, across all continents, average sperm concentration fell 51% between 1973 and 2018 (from about 100 M/mL to about 49 M/mL)Total sperm count fell 62% over the same periodThe decline is speeding up: the yearly fall has been steeper since 2000Chinese data point the same way: Huang 2017, in *Fertility and Sterility*, analyzed semen quality in 30,636 young men from 2001 to 2015 and also found a declineSuspected causes: endocrine-disrupting chemicals (bisphenol A, phthalates), obesity, sitting too much, heat and processed food. These are suspects; none has been shown to be the main cause
How male fertility changes with age:
After 35, sperm DNA damage (the DNA fragmentation index, DFI) increasesAfter 40, sperm count and motility decline slowlyAfter 45, new mutations become more frequent; a father's age above 45 is associated with a slightly higher risk of autism and schizophrenia in the childEven so, a 70-year-old man can still father a child; the curve is far flatter than a woman's
The main outside factors that harm sperm:
1. Heat: the testes need to be 2–3°C cooler than the body core. Long sitting, tight underwear, a laptop on the lap, and repeated saunas or hot baths all warm them and reduce sperm production. After these habits stop, it takes one sperm-production cycle (about 3 months) for recovery to show
2. Smoking: more DNA damage, worse shape, lower concentration. After quitting, sperm measures usually improve within 3–6 months
3. Heavy drinking: it suppresses the testosterone-making cells in the testes (Leydig cells), so testosterone falls, and alcohol is also directly toxic to sperm. A systematic review of observational studies (Salas-Huetos 2017) also lists alcohol among the dietary factors linked with poorer semen quality. There is no level of drinking that is safe for health; less is better
4. Obesity ( above 30): in observational studies, men with obesity have worse semen measures overall. The mechanism: fat tissue converts androgens into (aromatization), and higher estradiol damps down the hypothalamic–pituitary–gonadal axis, on top of higher local temperature. Some studies report improved sperm measures after losing 5–10% of body weight
5. Endocrine-disrupting chemicals: bisphenol A in plastic bottles, can linings and thermal receipt paper; phthalates in soft plastics, cosmetics and fragrance; per- and polyfluoroalkyl substances (PFAS, the "forever chemicals") in non-stick pans, waterproof clothing and food packaging; pesticides (glyphosate, organophosphates, pyrethroids) as residues on food. The evidence for their effects on human sperm is mostly observational. In practice: use less plastic, store food in glass, use fewer non-stick pans, choose organic produce more often, and eat less processed food
6. Chronic disease: diabetes and high blood pressure affect sperm directly and through their medicines; an underactive or overactive thyroid disturbs the hypothalamic–pituitary–gonadal axis; depression and chronic stress suppress it through the stress axis; men with obstructive sleep apnea () often have low testosterone. Getting chronic disease under control may partly restore fertility
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Evidence · What improves sperm quality
Ways to improve sperm quality, ranked by strength of evidence:The most consistent evidence is for lifestyle: quitting smoking, weight loss in men with obesity, moderate (not extreme) exercise, and drinking less. The support comes mostly from observational studies plus a plausible mechanism, and the benefit to overall health is certain.Some trial signal: antioxidant combinations (vitamin C, vitamin E, zinc, selenium, , L-carnitine and others), where a 2019 Cochrane review found a possible partial benefit with low-certainty evidence; omega-3; enough vitamin D.Weak evidence, mostly marketing: maca has small positive trials with modest effects; D-aspartic acid has a weak signal; ashwagandha has one small positive trial in men with low sperm counts (Ambiye 2013); the many "male vitality" and "sperm-boosting" blends are heavily marketed with thin evidence.
Sperm banking and freezing:
Before chemotherapy or radiotherapy: preserve fertility firstPlanning to become a father later (35 and up): an option, but because sperm are made continuously it is not as necessary as egg freezingSurvival after thawing: about 60–80% with modern freezing methods
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Chapter 2
Folate and the closing neural tube
One of the embryo's first big moves is to roll the early brain and spinal cord into a tube. It starts as a flat plate on the embryo's back. The two sides lift into a groove, and the groove's edges close from the middle toward the head and tail ends, like a zipper being pulled shut. The hollow tube left inside becomes the brain and spinal cord.
That zipper has only a few days, in the third to fourth week after fertilization, when most women do not yet know they are pregnant. That is why folate should start 3 months before conception: the raw materials have to be in place before the zipper starts.
Folate's job here is specific. A cell must copy its entire DNA before it divides, and two kinds of DNA building blocks (purines and thymine) can only be assembled if folate carries carbon atoms to them step by step. In these few days, neural-tube cells divide faster than any others in the embryo. If folate cannot keep up, the building blocks run short and the zipper can stall at some point along its length. Stalling at the head end and stalling at the tail end have completely different consequences.
[Watch the neural tube close, day by day](./neural-tube): the four steps between days 17 and 28 after fertilization, and why closure fails when folate is short.
That zipper has only a few days, in the third to fourth week after fertilization, when most women do not yet know they are pregnant. That is why folate should start 3 months before conception: the raw materials have to be in place before the zipper starts.
Folate's job here is specific. A cell must copy its entire DNA before it divides, and two kinds of DNA building blocks (purines and thymine) can only be assembled if folate carries carbon atoms to them step by step. In these few days, neural-tube cells divide faster than any others in the embryo. If folate cannot keep up, the building blocks run short and the zipper can stall at some point along its length. Stalling at the head end and stalling at the tail end have completely different consequences.
[Watch the neural tube close, day by day](./neural-tube): the four steps between days 17 and 28 after fertilization, and why closure fails when folate is short.
Mechanism · The neural tube closes in four steps
One of the most critical windows in embryonic development falls at days 21–28 after fertilization: neural-tube closure.The embryology, day by day:
Days 17–19 after fertilization: the neural plate forms in the outer germ layer (ectoderm)Days 20–22: the plate folds up into a groove (the neural groove)Days 23–26: the edges of the groove meet and zip shut from the middle toward both endsBefore day 28: the tube should be fully closed; it then develops into the brain and spinal cord
When closure fails, the result is a neural-tube defect (NTD). Low folate is one of its main preventable risk factors:
Anencephaly: the head end fails to close; the fetus has no cerebral hemispheres, and most are stillborn or die soon after birthSpina bifida: the tail end fails to close; nerve damage varies, and severe cases include paralysis of the legs and loss of bladder and bowel controlEncephalocele: a gap in the skull through which brain tissue bulges out
Evidence · Two trials that changed public health
Using folate to prevent neural-tube defects is one of the best-supported public-health wins of modern medicine. It rests on two :MRC 1991 (*The Lancet*): the participants were women at high risk because they had already had a pregnancy affected by a neural-tube defect. Taking 4 mg of folic acid a day cut the risk of it happening again by 72%; a mixture of 7 other vitamins, tested at the same time, showed no protective effect.Czeizel 1992 (*The New England Journal of Medicine*): the participants were women from the general population. Starting a multivitamin containing 0.8 mg of folic acid before conception brought first-occurrence neural-tube defects down to 0 (no cases in the supplement group, several in the control group).The mechanism: folate feeds one-carbon metabolism, supplying the carbon for making purines and thymine, so DNA copying can keep pace with how fast neural-tube cells divide. Part of the effect also runs through methylation and the pathway (see folate).
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Evidence · What fortifying flour achieved
What happened when folate went into staple foods:From 1998 the United States required enriched cereal-grain products to carry 0.14 mg of folic acid per 100 g. Afterward, the birth prevalence of anencephaly and spina bifida fell by about 28% (35% in surveillance programs that also record prenatal diagnoses), which means about 1,326 fewer affected births each year (Williams 2015, CDC's weekly report)According to the Crider 2022 review, 71 countries require folic acid in staple foods, including Canada, Chile, Costa Rica and Australia; the reported drops in neural-tube defects reach as high as 78%Most European countries have no mandatory fortification, their neural-tube defect rates have not fallen much, and the policy debate continuesSince 2009, China has handed out free folate (0.4 mg a day) widely to women of reproductive age. Neural-tube defects fell clearly in rural areas, but a gap between cities and the countryside remains
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Myth · The folate trap and the MTHFR debate
Folate is more complicated than most people assume. Here are the common controversies, one at a time.Controversy 1: the folate trap
At high doses, unmetabolized folic acid (UMFA) builds up in the blood. That is real, but whether it has clinical consequences is unclear from the evidenceThe real danger is masking vitamin B12 deficiency. Folate corrects the megaloblastic anemia that B12 deficiency causes, while the nerve damage keeps progressing and eventually becomes irreversibleThe fix: vegetarians and vegans, older adults, and people with low stomach acid should have their B12 checked when they take folate
Controversy 2: gene testing
The MTHFR C677T polymorphism lowers the enzyme's activity, most in TT homozygotes and moderately in CT heterozygotes. How common it is varies sharply by ancestry: NIH ODS puts TT homozygosity at about 25% of Hispanics, about 10% of Caucasians and Asians, and about 1% of African AmericansThe sales line "if you have the MTHFR variant, you must take active folate ()" stretches the evidence too farIn reality, a standard 400 μg of folic acid still prevents neural-tube defects in people with the TT type; what matters is getting enough5-MTHF (sold under brand names such as Quatrefolic and Metafolin) costs considerably more, with little added clinical benefit
Controversy 3: can fortified foods push folate too high?
The worry: in the United States, fortified staples plus personal supplements can push folate intake above 1 mg a dayOne specific concern is masking B12 deficiency in older adults, which the CDC and other agencies keep monitoringAnother is a possible link with colon or prostate cancer. Large cohort studies have not shown a clear association, but it is still actively studiedThe consensus: for women of reproductive age, the benefit far outweighs the possible risk, and fortification policy has been stable for 30 years
In practice:
All women trying to conceive, and in early pregnancy: 0.4–0.8 mg of folate a day; a multivitamin that also contains B12 and B6 is a reasonable choiceThe original 1992 text from the US Centers for Disease Control and Prevention (CDC) pairs the 0.4 mg figure with a ceiling: keep total folate intake below 1 mg a day unless a doctor is supervising, precisely because of the B12 masking in Controversy 1The randomized-trial evidence for 4 mg a day comes only from women who have already had a pregnancy affected by a neural-tube defect (MRC 1991). The CDC text leaves that decision to a doctor and notes that 0.4 mg may work just as well. It is not a dose to step up to on your ownAntiepileptic drugs, or type 1 or type 2 diabetes: the UK NICE 2025 guideline offers these two groups a high dose, but it is started by an obstetrician or neurologist, not by the readerA higher body mass index () on its own is not a reason to raise the dose: after reviewing the evidence, NICE 2025 states that 400 μg is enough unless one of the risk factors above appliesThe MTHFR genotype is not a reason to raise the dose: at 400 μg a day, red-cell folate responds almost identically across genotypes (Crider 2022), and the American College of Medical Genetics and Genomics (ACMG) does not recommend routine testingMen: in observational studies, men with more folate in their diet had better semen measures (the Salas-Huetos 2017 systematic review). That is an association, not the result of a supplement trialThere is no need to agonize over natural versus synthetic. Synthetic folic acid has the strongest randomized-trial evidence for preventing neural-tube defects. Folate in food (mostly 5-MTHF) works just as well, but reaching 400–800 μg from food alone is hard
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Chapter 3
Why pregnancy needs more iron
Pregnancy makes your body do three iron-hungry jobs at once: store enough iron in the baby to last until solid food begins, grow an entire placenta, and make a large amount of extra blood of your own. Iron sits at the core of hemoglobin, the oxygen-grabbing protein inside red blood cells, and the iron for all three jobs comes out of your blood.
One thing is easy to misread. In pregnancy the fluid part of the blood (plasma) expands faster than the red cells, so the same red cells are spread through more water and hemoglobin on a lab report drifts down a little. This is physiological dilution, not anemia.
Real iron deficiency means the stores have been drained. The placenta moves iron to the baby first and the mother comes second, so your stores empty first: you feel tired, and you are more likely to bleed heavily during and after birth. For the baby, iron is raw material for myelin, the sheath wrapped around nerve fibers like insulation on a wire, and if that step is delayed it may not be fully made up later. More is not better either: in observational studies, hemoglobin that runs too high in pregnancy is linked with a baby who grows too little, so women who are not iron deficient do not need to push the dose up.
One thing is easy to misread. In pregnancy the fluid part of the blood (plasma) expands faster than the red cells, so the same red cells are spread through more water and hemoglobin on a lab report drifts down a little. This is physiological dilution, not anemia.
Real iron deficiency means the stores have been drained. The placenta moves iron to the baby first and the mother comes second, so your stores empty first: you feel tired, and you are more likely to bleed heavily during and after birth. For the baby, iron is raw material for myelin, the sheath wrapped around nerve fibers like insulation on a wire, and if that step is delayed it may not be fully made up later. More is not better either: in observational studies, hemoglobin that runs too high in pregnancy is linked with a baby who grows too little, so women who are not iron deficient do not need to push the dose up.
Numbers · How much more iron pregnancy needs
Pregnancy is when a healthy adult woman's iron need is highest. Under the Chinese national standard (WS/T 578.3—2017), the recommended nutrient intake () rises from 20 mg/day for a woman who is not pregnant to 24 in the second trimester and 29 mg/day in the third; a man of the same age needs 12.Two things are easy to mix up. The RNI is not the : the estimated average requirement (EAR) is the median need of the population (15 for non-pregnant women, 22 in late pregnancy). It always sits one step below the RNI, and mixing the two invents four or five milligrams out of nowhere. And the need does not double: late pregnancy compared with not pregnant is 29 ÷ 20 ≈ 1.45 times, and compared with a man of the same age ≈ 2.4 times.
⚠️ The other pair of figures you often see (women 18, pregnancy 27) is the US Recommended Dietary Allowance (). The two standards assume different diets and different iron absorption, so their numbers are not supposed to match. When they disagree, first ask whose standard this is.
Five things drive the rise in need:
1. The baby's iron stores: a full-term newborn holds about 270–300 mg of iron in the liver to last the 4–6 months until solid food starts, and all of it comes from the mother
2. The placenta and umbilical cord: about 90 mg of iron
3. The mother's blood volume rises 45–50%: the total mass of red cells rises too, but plasma rises more, which produces physiological dilution
4. Blood lost at birth: about 500 mL for a vaginal birth and about 1000 mL for a cesarean
5. Breastfeeding: breast milk is not rich in iron (about 0.3 mg/L), but nursing delays the return of periods and so cuts menstrual iron loss
Clinical · How much to take, and the cost of too little
WHO's 2016 antenatal care recommendations:Routine iron in pregnancy, 30–60 mg a day, plus 0.4 mg of folic acid, for the whole pregnancyThat is the default. Where anemia is uncommon among pregnant women, or when daily iron causes side effects that cannot be tolerated, intermittent supplementation (not every day, with the dose set by a doctor) is also an option
What iron-deficiency anemia in pregnancy costs:
The mother: fatigue, and a higher risk of heavy bleeding during and after birthThe baby: preterm birth, low birth weight, and slower cognitive development in infancy. Iron is a key raw material for the myelin that forms around an infant's nerves; in observational studies with long follow-up, these children scored on average 1–2 IQ points lower, and the gap was hard to close laterThe other direction also causes trouble: in observational studies, hemoglobin above 130 g/L in pregnancy is linked with fetal growth restriction, so more is not better
In practice · Taking iron so it gets absorbed
The practical traps of taking iron:Form: ferrous sulfate and ferrous fumarate (ferrous iron, Fe²⁺) work better than ferrous gluconate; polysaccharide-iron complex is a little weaker; the newer ferric maltol has fewer side effectsIron is absorbed best on an empty stomach, which is also when it upsets the stomach most. Taking it every other day (Stoffel 2017) gave higher total absorption than daily dosing in women who were iron-depleted, not anemic and not pregnant. Daily iron makes the liver release more hepcidin, a hormone that closes the gate on iron absorption, and a day off gives it time to fall back (see iron). In pregnancy, follow your obstetrician on exactly how to take itTake it with vitamin C: vitamin C in the same meal clearly improves absorption of non-heme ironKeep it at least 2 hours away from calcium, tea, coffee, milk and antacidsSide effects: constipation, black stools and stomach upset. Halve the dose or change the form; if the problems continue, talk to your doctor about intravenous ironSevere deficiency (hemoglobin below 90 g/L) is hard to correct by mouth, and intravenous iron (such as ferric carboxymaltose) is often considered to correct it in one go
Myth · Does donkey-hide gelatin rebuild blood
On herbal teas, bird's nest and donkey-hide gelatin (ejiao) to build blood in pregnancy: in traditional Chinese medicine, ejiao is regarded as a blood tonic, but its iron content is low (about 0.2 mg/g dried). By food-composition data, pork liver, beef, clams and fortified cereals contain 10–100 times more iron than ejiao.Chapter 4
Where the baby's brain gets DHA
A baby's brain and eyes are built with a fat called as a building material. It is not fuel to be burned but a structural part: DHA slots into the membranes of nerve cells and makes them softer and easier to bend, which lets signals travel fast. The retina holds an especially high share of this fat, because seeing is itself a chain of very fast signals.
The trouble is that a fetus can barely make DHA itself. The shorter relative found in plant oils (alpha-linolenic acid, ) has to be lengthened step by step in the liver to become DHA, and in the fetus that production line is mostly switched off. So nearly all the DHA in the baby's brain is carried across the placenta from your blood; if your blood does not have it, the placenta cannot pass it on.
The best source is fish, but fish also carry mercury, which travels the same route into the baby's brain. This is one of the hardest balancing acts in pregnancy nutrition. The answer is not to avoid fish: in a large British observational study, mothers who ate little fish in pregnancy were more likely, not less, to have children with low verbal IQ. What to do is choose fish that are low in mercury.
The trouble is that a fetus can barely make DHA itself. The shorter relative found in plant oils (alpha-linolenic acid, ) has to be lengthened step by step in the liver to become DHA, and in the fetus that production line is mostly switched off. So nearly all the DHA in the baby's brain is carried across the placenta from your blood; if your blood does not have it, the placenta cannot pass it on.
The best source is fish, but fish also carry mercury, which travels the same route into the baby's brain. This is one of the hardest balancing acts in pregnancy nutrition. The answer is not to avoid fish: in a large British observational study, mothers who ate little fish in pregnancy were more likely, not less, to have children with low verbal IQ. What to do is choose fish that are low in mercury.
Mechanism · Why the baby's DHA comes from the mother
From mid-to-late pregnancy until age 2, the baby's brain and retina need at a soaring rate: about 15–20% of the fatty acids in the brain's gray matter are DHA, and about 50% of the fatty acids in the membranes of the retina's light-sensing cells. That DHA has to come from the mother's blood. The fetus can make almost none, and even in adults, usually less than 1% of the plant fat alpha-linolenic acid () gets lengthened into DHA.The American College of Obstetricians and Gynecologists (ACOG), WHO and the Food and Agriculture Organization (FAO) recommend, for pregnancy and breastfeeding, at least 200–300 mg a day of DHA plus , the other long-chain fatty acid in fish oil. Two to three servings a week of low-mercury fish cover it. For DHA alone, at least 200 mg a day is a safe target.
In practice · Which fish to eat in pregnancy
Fish is the best source of , but it carries a mercury risk. In 2021 the US Food and Drug Administration (FDA) and Environmental Protection Agency (EPA) sorted common fish into three groups:Best choices (2–3 servings a week, each about 4 ounces, a little over 100 g): cod, salmon, sardines, anchovies, freshwater trout, tilapia, haddock, Atlantic mackerel, black sea bass, Atlantic croaker, flounder, hake, and canned light tuna. These are low in mercury, and the oily ones among them, such as salmon, sardines and mackerel, are also high in DHA.
Good choices (1 serving a week): carp, white (albacore) tuna, canned or fresh, and yellowfin tuna.
Avoid (highest mercury): shark, swordfish, bigeye tuna, tilefish from the Gulf of Mexico, king mackerel, marlin and orange roughy.
Tuna depends on the kind: canned light tuna is a best choice, white tuna is once a week, and bigeye tuna is one to avoid.
Evidence · Weighing mercury against DHA
Weighing mercury against : the British ALSPAC cohort (Hibbeln 2007, *The Lancet*) followed about 12,000 pregnant women and their children. Compared with mothers who ate more than 340 g of seafood a week in pregnancy (12 ounces, the US limit advised at the time), mothers who ate less were more likely to have children whose verbal IQ fell in the lowest quarter for their age, and the risk was highest for mothers who ate none. This was an observational study, so it shows an association, but it challenged the old advice that "the less fish in pregnancy, the safer". The FDA then revised its guidance in 2014 and 2021 to encourage eating low-mercury fish rather than simply avoiding fish. The current consensus is that the DHA and other nutrients lost by eating no fish do more harm than the mercury from a moderate amount of low-mercury fish.Fish oil or real fish:
Real fish beats fish oil: it also brings protein, selenium, iodine, vitamin D and a whole fat matrixFor pregnant women who do not eat fish, Fish Oil or algal-oil DHA is a reasonable substitute; algal DHA is a vegan source, contains no mercury, and is often preferredInfant formulas have started adding DHA and arachidonic acid (ARA). There are randomized trials, but a 2017 Cochrane found inconsistent results for thinking and vision outcomes
Myth · Are DHA gummies and megadoses worth it
The marketing traps of pregnancy gummies and high-dose supplements:Two meals of oily fish a week usually reach the target of about 200 mg of DHA a day, so gummies are not neededVery high doses (over 1000 mg) have shown no extra benefit for the baby. Omega-3 fats mildly slow down platelets, so ask your obstetrician before taking large doses" lifts your mood" and "DHA makes the baby smarter" are both oversold. The evidence supports enough, not the more the better
Chapter 5
Menopause and falling testosterone
Menopause is often described as "the hormones are gone". What makes people feel unwell is not the word gone. It is that estrogen had been working in several places at once for years, and when it withdraws, all those posts fall empty together.
Its receptors are not only in the uterus and ovaries; they sit on cells in bone, the lining of blood vessels, the brain and the urogenital tract. So when estrogen leaves, the bone cells whose job is to break bone down (osteoclasts) lose their brake and remove bone faster than it is rebuilt, so falls. The lining of the blood vessels loses a layer of protection. The brain is full of estrogen receptors, so complaints about mood and memory follow. The lining of the urogenital tract becomes thinner and drier. Hot flashes and night sweats come from blood vessels in the skin repeatedly widening and narrowing.
For men it is a gentle slope, not a cliff: testosterone falls slowly, year by year, from middle age. And many symptoms blamed on low testosterone actually come from weight, sleep and chronic illness, not from testosterone itself.
Its receptors are not only in the uterus and ovaries; they sit on cells in bone, the lining of blood vessels, the brain and the urogenital tract. So when estrogen leaves, the bone cells whose job is to break bone down (osteoclasts) lose their brake and remove bone faster than it is rebuilt, so falls. The lining of the blood vessels loses a layer of protection. The brain is full of estrogen receptors, so complaints about mood and memory follow. The lining of the urogenital tract becomes thinner and drier. Hot flashes and night sweats come from blood vessels in the skin repeatedly widening and narrowing.
For men it is a gentle slope, not a cliff: testosterone falls slowly, year by year, from middle age. And many symptoms blamed on low testosterone actually come from weight, sleep and chronic illness, not from testosterone itself.
Mechanism · What follows when estrogen falls
Menopause in women (ages 45–55) and the decline of androgens in men (about −1% a year from 35) make up the stage of life where hormones and nutrition meet most densely.Menopause in women
The core change is the ovaries winding down: after menopause estrogen falls by about 90%, progesterone falls with it, and a chain of downstream changes follows:
Faster bone loss: estrogen had been supporting the bone-building cells (osteoblasts) and restraining the bone-removing cells (osteoclasts). Once it is gone the osteoclasts lose their brake, and can fall by about 20% within 5–10 years (see calcium)Higher cardiovascular risk: estrogen had been protecting the lining of blood vessels and keeping low-density lipoprotein () cholesterol lowerHigher risk of metabolic syndrome: more fat around the organs and worsening insulin resistanceGenitourinary atrophy: vaginal dryness and repeated urinary tract infectionsVasomotor symptoms: hot flashes, night sweats and insomnia, experienced by about 70–80% of women and lasting about 7 years on averageMood swings and complaints about memory and thinking: estrogen receptors are spread widely through the brain
Evidence · Menopause nutrition and training
Nutrition and lifestyle with evidence behind them:Calcium 1200 mg a day and vitamin D 800–1000 a day, together, slow bone loss (see calcium). Vitamin is often recommended alongside, at 100–180 μg a day, but its trial evidence for bone is weaker than that for calcium and vitamin DStrength training (resistance training) 2–3 times a week is something no supplement can replace, because it works on bone and muscle at the same timeSoy isoflavones: the Cochrane review (Lethaby 2013) concluded there is no conclusive evidence that plant estrogens reduce how often or how badly hot flashes occur. The one signal worth watching is high-dose genistein (over 30 mg a day), which did lower hot-flash frequency in 4 trials. But those 4 were not pooled, and the authors called it worth further study, not effective. So it is unproven, not a mild form of hormone therapyLess alcohol and no smoking: both speed up bone loss
Clinical · Hormone therapy and its time window
The time window for menopausal hormone therapy (): after the large from the Women's Health Initiative (WHI) was published in 2002 (Rossouw 2002, *JAMA*), use of hormone therapy dropped sharply. But the women in that trial were older (63 on average), and most were already far past menopause. The 2022 position statement of the North American Menopause Society (NAMS 2022) holds that for women under 60, or within 10 years of menopause, without contraindications, the benefits of hormone therapy for bothersome hot flashes and night sweats and for preventing bone loss outweigh the risks. So it is not "hormones are forbidden for life" but "check the time window, then decide for the individual", with a doctor's assessment.nams-2022-mht-position
Mechanism · How male testosterone slowly declines
The decline of male androgens (some call it male menopause, or andropause, but the term is not quite accurate)From age 35, total testosterone falls about 1% a year, adding up to about −30% on average by 65Low testosterone is not the same as symptomatic testosterone deficiency. In most older men the decline is slow and most stay in the lower half of the normal range; common symptoms often come from obesity, low mood or chronic disease rather than from testosterone itselfOnly true symptomatic primary or secondary hypogonadism, where the testes or the pituitary gland above them fail and testosterone really is too low, is a medical reason to replace testosterone
In practice · What actually raises testosterone
The real diet and lifestyle levers on male testosterone, strongest first:1. Lose weight, alongside strength training. In the European Male Ageing Study (EMAS) cohort, men who lost weight saw testosterone rise in proportion, and men who gained weight saw it fall in proportion (Camacho 2013). That is an observed association, but it is the strongest item on this list. No percentage is given here on purpose: the often-quoted " from 30 to 25 raises testosterone 20–30%" is not a figure that paper reported
2. Sleep 7–8 hours. In a small trial of 10 healthy young men (Leproult 2011), sleeping only 5 hours a night for 1 week lowered daytime testosterone by 10–15%
3. Stop smoking and drink less
4. Get enough zinc (see zinc). Zinc deficiency does lower testosterone; in men who already have enough zinc, there is no evidence that more raises it further
5. Get enough vitamin D. Some studies show testosterone improves when a deficiency is corrected, but the are weak
6. "Natural testosterone boosters": D-aspartic acid, fenugreek, Tribulus, deer antler and the like mostly have weak randomized-trial evidence or results that did not replicate
"Male menopause" supplements are one of the most oversold product categories. What actually changes testosterone is weight, sleep, exercise and quitting smoking, not a pill.
leproult-2011-sleep-restriction-testosterone
Chapter 6
How age affects fertility
Why does age hold fertility down? The answer is not a vague "the body gets old" but one very specific thing: the egg.
While a girl is still in her mother's womb, all her eggs are made at once, and after that their number only falls. More important, every egg waits paused halfway through a cell division, like a video frozen on one frame, for decades. Only when it is woken in some later month does it go on to finish that division.
The problem lies in those decades of waiting. The egg is exposed to damage the whole time, collecting errors bit by bit. When it finally has to pull its paired chromosomes apart, the chance of getting the split wrong rises with the years it has waited. Embryos with the wrong number of chromosomes mostly stop developing very early, which shows up as never getting pregnant or a very early miscarriage.
So what age mainly holds down is not how many eggs are left but how accurate the remaining ones are. For men, the change is a gentle slope, not a cliff.
While a girl is still in her mother's womb, all her eggs are made at once, and after that their number only falls. More important, every egg waits paused halfway through a cell division, like a video frozen on one frame, for decades. Only when it is woken in some later month does it go on to finish that division.
The problem lies in those decades of waiting. The egg is exposed to damage the whole time, collecting errors bit by bit. When it finally has to pull its paired chromosomes apart, the chance of getting the split wrong rises with the years it has waited. Embryos with the wrong number of chromosomes mostly stop developing very early, which shows up as never getting pregnant or a very early miscarriage.
So what age mainly holds down is not how many eggs are left but how accurate the remaining ones are. For men, the change is a gentle slope, not a cliff.
Numbers · Chance of conceiving per cycle, by age
The curve linking age and fertility is rarely discussed in Chinese-speaking communities, but it should be explained early.A woman's chance of conceiving naturally in one menstrual cycle (commonly quoted clinical estimates; individuals vary a lot):
Ages 20–24: about 25–30%30: about 20%35: about 15%38: about 10%40: about 5%42: about 3%45: below 2%
The reason behind it: a girl is born with about 1–2 million oocytes, which fall to about 300,000 before puberty. After that, each menstrual cycle uses up about 1,000 (usually only one ovulates and the rest die off). By 40, about 20–30 thousand remain. It is not only the count that falls: the share of eggs with the wrong number of chromosomes rises from about 10% at 30 to about 50% at 40. This is the main reason the risks of miscarriage and Down syndrome rise with the mother's age.
Evidence · How male fertility changes with age
Male fertility falls more gently, but just as really:After 35, sperm DNA damage increasesNew mutations become more frequent (passed on from the father); a father's age above 45 is associated with a slightly higher risk of autism and schizophrenia in the childEven so, a 70-year-old man can still father a child; his count curve is far flatter than a woman's
Clinical · Can IVF make up for age
What assisted reproductive technology (ART) can do:Live-birth rate per cycle of in vitro fertilization (IVF) (the rough scale of US assisted-reproduction registry data; centers and years differ a lot):
Under 35: about 35–40%35–37: about 30%38–40: about 20%41–42: about 10%Over 42 (with her own eggs): about 3–5%
"IVF can buy back age" is a common misunderstanding. It raises the efficiency of each cycle; it cannot reverse the decline in egg quality. Elective egg freezing works best before 34; freeze after 38 and both the number of eggs retrieved and the later IVF success rate fall clearly. Preimplantation genetic testing for chromosome number (PGT-A) can help set aside some embryos with the wrong chromosome count, but whether it raises the final live-birth rate is still debated, and it cannot create a good embryo out of nothing.
In practice · A checklist for fewer regrets
Practical principles (a checklist for fewer regrets later):If you want children but plan to wait: consider one visit to a reproductive-medicine clinic. Anti-Müllerian hormone (AMH) and an ultrasound count of small resting follicles (antral follicle count) give a rough picture of ovarian reserve and predict roughly how many eggs egg freezing or IVF would yield, but they cannot predict the chance of getting pregnant naturally. This is not pressure; it is information for your own decisionTrying to conceive with regular sex: under 35, see an infertility clinic after 1 year without pregnancy; at 35 or older, go after 6 monthsUnsure when to have children: you can discuss egg freezing with a reproductive-medicine specialist; deciding early beats deciding lateMen aged 35–45 can also have a semen analysis; whether to add tests such as sperm DNA damage is the doctor's call. This is not only her issueIf you have a chronic disease or take long-term medicine, ask about pregnancy risks before you try
Background · Why there is no right age
The social facts:The costs of waiting: the money spent on infertility treatment, the risk of chromosomal problems, and the complications of pregnancy at an older ageThe costs of going early: career, finances, and whether a partnership is readyThere is no right age, but open information lets a person choose actively instead of finding out afterwards
The one line to take away: the biological clock is not patriarchal scare talk; it is a real physiological fact. It is not fate either. Know early, get assessed early, decide early, and a person can still make more choices within the biological limits.
References · 14
- American College of Obstetricians and Gynecologists. (2021). Nutrition During Pregnancy (FAQ001) and Committee Opinion 762: Prepregnancy Counseling. www.acog.org/womens-health/faqs/nutrition-during-pregnancy
- World Health Organization. (2016). WHO recommendations on antenatal care for a positive pregnancy experience. WHO Press. www.who.int/publications/i/item/9789241549912
- MRC Vitamin Study Research Group. (1991). Prevention of neural tube defects: results of the Medical Research Council Vitamin Study. The Lancet, 338(8760), 131-137. Factorial RCT at 33 centres in 7 countries: 1,817 women at high risk because of a previous NTD-affected pregnancy, randomized to folic acid, a mixture of 7 other vitamins, both, or neither. NTDs: 6 in the folic acid groups vs 21 in the others, a 72% protective effect (RR 0.28, 0.12-0.71); the other vitamins showed no significant protective effect (RR 0.80) (abstract, PMID 1677062). 10.1016/0140-6736(91)90133-A
- Centers for Disease Control and Prevention. (1992). Recommendations for the use of folic acid to reduce the number of cases of spina bifida and other neural tube defects. MMWR Recommendations and Reports, 41(RR-14), 1-7. www.cdc.gov/mmwr/preview/mmwrhtml/00019479.htm
- National Health and Family Planning Commission of the People's Republic of China. (2017). Chinese dietary reference intakes - Part 3: Trace elements (WS/T 578.3-2017). Health industry standard, issued 2017-09-14, effective 2018-04-01; drafted by the Chinese Nutrition Society with the National Institute for Nutrition and Health, China CDC. Covers the seven essential trace elements iron, iodine, zinc, selenium, copper, molybdenum and chromium. Table 1, iron in mg/d as EAR / RNI: men 18 and over 9 / 12; women 18-49 15 / 20; women 50 and over 9 / 12; pregnancy weeks 1-12 15 / 20, weeks 13-27 19 / 24, week 28 onward 22 / 29; lactation 18 / 24; UL 42 for all adult groups. Also: zinc RNI 12.5 mg/d men and 7.5 mg/d women, selenium RNI 60 micrograms/d, iodine RNI 120 micrograms/d for adults. The standard defines EAR and RNI as distinct quantities - EAR is the group median requirement, RNI the level meeting the needs of nearly all individuals - so the two must not be used interchangeably. www.nhc.gov.cn/ewebeditor/uploadfile/2017/10/20171017153105952.pdf
- National Institutes of Health, Office of Dietary Supplements. (2024). Iron — Fact Sheet for Health Professionals. Fact sheet (updated September 4, 2025; Wayback snapshot 21 September 2026): RDAs 8 mg/day for men and for women 51+, 18 mg women 19-50, 27 mg pregnancy; UL 45 mg/day from age 14; bioavailability about 14%-18% from mixed diets with meat, seafood and vitamin C and 5%-12% from vegetarian diets; serum ferritin below 30 mcg/L suggests iron deficiency and below 10 mcg/L IDA, but inflammation can raise ferritin; supplemental iron of 45 mg/day or more may cause nausea and constipation; people with hereditary hemochromatosis are at risk of iron overload (fact sheet). Heme vs nonheme: heme iron (lean meat and seafood are the richest sources) has higher bioavailability than nonheme iron, and other dietary components affect it less; calcium might reduce the bioavailability of both forms; heme iron is about 10%-15% of total iron intake in western populations. The sheet gives no separate heme and nonheme absorption percentages (fact sheet, Wayback 2026 snapshot). ods.od.nih.gov/factsheets/Iron-HealthProfessional
- Stoffel, N. U., Cercamondi, C. I., Brittenham, G., Zeder, C., Geurts-Moespot, A. J., Swinkels, D. W., et al. (2017). Iron absorption from oral iron supplements given on consecutive versus alternate days and as single morning doses versus twice-daily split dosing in iron-depleted women: two open-label, randomised controlled trials. The Lancet Haematology, 4(11), e524-e533. Cumulative fractional iron absorption was higher with alternate-day dosing (~21.8%) than consecutive-day dosing (~16.3%). Study 1 (40 iron-depleted women, 60 mg at 08:00 on 14 consecutive days vs on alternate days for 28 days): cumulative fractional absorption 16.3% vs 21.8% (p = 0.0013), total absorbed 131.0 vs 175.3 mg; hepcidin higher on consecutive days (p = 0.0031). Study 2 (20 women, 10 per group, then crossed over; 120 mg once daily vs 60 mg twice daily for 3 days): no significant difference in fractional (11.8% vs 13.1%, p = 0.33) or total absorption (44.3 vs 49.4 mg, p = 0.33), but twice-daily split dosing raised serum hepcidin (p = 0.013). Authors: alternate-day single doses optimise absorption and might be preferable; to be confirmed in iron-deficient anaemic patients. Corrected 2026-09-24: an earlier version of this record said single doses outperformed split dosing, which the abstract does not report (abstract, PMID 29032957). 10.1016/S2352-3026(17)30182-5
- Hibbeln, J. R., Davis, J. M., Steer, C., et al. (2007). Maternal seafood consumption in pregnancy and neurodevelopmental outcomes in childhood (ALSPAC study): an observational cohort study. The Lancet, 369(9561), 578-585. 10.1016/S0140-6736(07)60277-3
- U.S. Food and Drug Administration & EPA. (2021). Advice About Eating Fish: For Those Who Might Become or Are Pregnant or Breastfeeding and Children Ages 1 to 11 Years. www.fda.gov/food/consumers/advice-about-eating-fish
- Mozaffarian, D., & Wu, J. H. Y. (2011). Omega-3 fatty acids and cardiovascular disease: effects on risk factors, molecular pathways, and clinical events. Journal of the American College of Cardiology, 58(20), 2047–2067. 10.1016/j.jacc.2011.06.063
- Rossouw, J. E., Anderson, G. L., Prentice, R. L., et al. (2002). Risks and benefits of estrogen plus progestin in healthy postmenopausal women: principal results from the Women's Health Initiative randomized controlled trial. JAMA, 288(3), 321-333. 10.1001/jama.288.3.321
- Lethaby, A., Marjoribanks, J., Kronenberg, F., Roberts, H., Eden, J., & Brown, J. (2013). Phytoestrogens for menopausal vasomotor symptoms. Cochrane Database of Systematic Reviews, (12), CD001395. 10.1002/14651858.cd001395.pub4
- Camacho, E. M., Huhtaniemi, I. T., O'Neill, T. W., Finn, J. D., Pye, S. R., Lee, D. M., et al. (2013). Age-associated changes in hypothalamic-pituitary-testicular function in middle-aged and older men are modified by weight change and lifestyle factors: longitudinal results from the European Male Ageing Study. European Journal of Endocrinology, 168(3), 445-455. 10.1530/EJE-12-0890
- Teede, H. J., Tay, C. T., Laven, J. J. E., et al. (2023). Recommendations from the 2023 International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome. Fertility and Sterility, 120(4), 767-793. 254 recommendations and practice points. The full text (the simultaneous JCEM publication, PMC10505534) states: PCOS prevalence 10% to 13% (Rotterdam criteria); follicle number per ovary >= 20 in at least 1 ovary is the adult PCOM threshold; AMH may replace ultrasound in adults only; insulin resistance is a pathophysiological factor, but clinically available insulin assays are of limited clinical relevance and should not be used in routine care; inositol could be considered for metabolic measures with limited clinical benefit, metformin should be considered over inositol for hirsutism and central adiposity, and inositol for infertility should be considered experimental (abstract, PMID 37589624; full text, PMC10505534). 10.1016/j.fertnstert.2023.07.025