TL;DR

• Conception depends on your cycle (a six-day fertile window ending on ovulation) and your age, which is one of the strongest predictors of natural fecundability.
• Folate has the clearest, strongest preconception recommendation of anything in this article, because of its established role in preventing neural tube defects. Start it before you're trying, not after a positive test.
• Omega-3, selenium, zinc and vitamin D have evidence in both female and male reproductive research and are already in our Prenatal Core, though the literature doesn't establish one universal "fertility dose" for most of them.
• CoQ10 and myo-inositol come up often in fertility research, mostly in IVF or PCOS populations specifically, but neither is a universal requirement for someone trying to conceive naturally.
• This article covers natural conception, not IVF, and isn't medical advice.

Conception depends on timing, age, egg and sperm quality, underlying health and a fair amount of chance. Nutrition matters, but no supplement can guarantee pregnancy, and a lot of fertility marketing implies more certainty than the research actually supports. This post covers natural conception specifically. We're not covering IVF here, though some of the same nutrients come up in that research too.

What actually happens during conception

Pregnancy can only begin when sperm and egg are present at the same time. Once a month, one dominant follicle releases a mature egg (ovulation), which survives for around 24 hours. Sperm can survive in the reproductive tract for up to five days, which is why intercourse in the days before ovulation, not just on the day itself, can lead to conception.

A landmark 1995 study in the New England Journal of Medicine, tracking 221 women, found conception occurred within a six-day window ending on the day of ovulation. Probability ranged from about 10% five days before ovulation to around 33% on the day itself, dropping close to zero afterwards, though ovulation timing itself carries some real-world uncertainty, so this window is a strong guide rather than something you can pinpoint perfectly. Clinical guidance generally recommends regular intercourse across the fertile window rather than trying to identify one exact day. If fertilisation happens, the embryo implants in the uterine lining around 6 to 10 days later. Pregnancy tests usually become positive only after implantation, once enough hCG has been produced, which is why testing too early can give a false negative.

Age matters more than most supplements do

Female age remains one of the strongest predictors of natural fecundability. American Society for Reproductive Medicine figures suggest a healthy 30-year-old has roughly a 20% chance of conceiving in any given cycle; by 40, that's under 5%, reflecting changes in both the number and quality of available eggs.

A large Danish cohort study of over 2,800 women found fecundability holds fairly steady through the late 20s and early 30s, then declines more noticeably after 35, to around 77% of the rate seen at 20 to 24, a bit steeper for women who haven't given birth before. Many women in their late 30s and early 40s still go on to conceive, it may simply take longer. If it doesn't happen as quickly as hoped, that isn't a dead end: IVF, egg freezing and donor eggs exist and have helped millions of people build families. Fertility evaluation is generally recommended after 12 months of trying for women under 35, after six months for women 35 or older, and earlier still may be appropriate over 40 or where another fertility risk is already known. Male age also matters, generally more gradually, though the specific effect of paternal age on sperm DNA integrity is better supported by dedicated paternal-age research than by this particular cohort study.

Preconception nutrition should start before the positive test, not after

Some reproductive processes take time to unfold. Sperm production takes roughly 74 to 90 days, plus further maturation afterwards, so nutrient status today shapes sperm that won't be used for weeks. Egg development is more complex biologically, follicles exist for years before final maturation, so it's a simplification to say an egg simply "starts developing three months before ovulation." What's genuinely well-established is narrower and more specific: folate needs to be adequate before the neural tube forms, which happens in the first few weeks of pregnancy, often before someone knows they're pregnant. That's a real, specific reason to think about nutrition before you start trying. It isn't evidence that every nutrient, for both partners, needs exactly three months of lead time, that's a tidier story than the research actually supports.

Folate has the clearest recommendation here

Folate is involved in DNA synthesis, cell division and early embryonic development. Public health guidance recommends 400 mcg of folic acid daily from when you start trying to conceive through 12 weeks of pregnancy, based on established evidence for preventing neural tube defects. That's stronger, more specific evidence than exists for most other supplements discussed in fertility circles.

Worth being precise here: the major outcome evidence for preventing neural tube defects is specifically for folic acid. Our Prenatal Core uses Quatrefolic®, an active form of folate (5-MTHF), which we've written about separately, it's well absorbed and avoids the conversion step folic acid requires, but we wouldn't claim it carries the identical, directly-studied neural-tube-defect prevention evidence that folic acid itself has accumulated over decades of public health data.

Nutrients with evidence in both sexes

A few nutrients show up in both female and male reproductive research, and are already part of our Prenatal Core.

Omega-3 (EPA and DHA) has evidence in both female and male reproductive research. In a University of North Carolina cohort study of 900 women trying to conceive, those taking omega-3 supplements had 1.51 times the odds of conceiving in a given cycle (95% CI 1.12-2.04), after adjusting for age, BMI, race, prior pregnancy and multivitamin use. Because this was observational, it can't prove omega-3 itself caused the difference. A 2024 meta-analysis (Trop-Steinberg et al., Heliyon) pooling both natural-conception and fertility-treatment studies also found better pregnancy and fertilisation outcomes associated with omega-3 intake, though heterogeneity across the pooled studies was high, so this doesn't establish that prescribing omega-3 itself raises conception rates in otherwise healthy women. On the male side, omega-3 is one of several nutrients associated with improved sperm concentration in the meta-analysis referenced below.

Selenium has been studied in both female and male fertility research, though the female evidence sits within a pooled antioxidant analysis (alongside vitamin E, vitamin C, N-acetylcysteine and others in a Cochrane review) rather than a selenium-specific trial, so it doesn't establish a selenium-specific conception benefit on its own.

Zinc and vitamin D are foundational to reproductive health generally, and both are already in Prenatal Core, but we'd be overstating things to call either a proven conception booster for women specifically. Zinc's clearest fertility-specific evidence here comes from the male sperm-quality data below. Because these nutrients are already present in Prenatal Core, you don't necessarily need to add separate supplements simply because they appear in fertility research, but that isn't the same as saying the doses in any one supplement have been established as an optimal fertility dose. No such dose exists in the literature for most of these.

Two supplements you'll encounter in fertility research: CoQ10 and myo-inositol

Neither of these is part of our Prenatal Core, and neither should be treated as a universal requirement for someone trying to conceive naturally. Here's what the evidence actually shows for each.

Coenzyme Q10 (CoQ10)

CoQ10 supports mitochondrial energy production inside developing eggs. Natural levels decline with age, alongside egg quality, though that's a parallel, not a proven cause-and-effect relationship. The most-cited trial, in 186 women under 35 with diminished ovarian reserve undergoing IVF, found CoQ10 pretreatment led to more retrieved eggs, a higher fertilisation rate, and far fewer embryo transfers cancelled for poor development.

Worth being precise about the limits here. That trial used 600 mg per day for 60 days, not a smaller "wellness" dose, and doses across the wider CoQ10 fertility literature vary substantially with no single established standard. The women studied were undergoing IVF with diminished ovarian reserve specifically, not healthy women trying to conceive naturally, so the underlying biology is relevant more broadly, but efficacy in natural conception is much less certain than in that specific population. Both ubiquinone and ubiquinol are used in supplements, and fertility trials haven't established that one produces better outcomes than the other.

The broader evidence base is a 2020 Cochrane review pooling 63 trials and 7,760 subfertile women taking various antioxidants, including CoQ10. It found antioxidant use was associated with higher live birth rates, but rated the certainty of that evidence as very low. For transparency: six of the pooled trials were later retracted and two more received expressions of concern from their journals; the review authors judged this didn't materially change the overall conclusion, but it's worth knowing.

If you're considering CoQ10, dose and timing are worth discussing with a fertility clinician rather than treating any one number as standard. Pregnancy safety data for CoQ10 are limited, so whether to continue after conception is also worth raising with your doctor.

Myo-inositol

Myo-inositol is involved in how cells respond to insulin and to the hormones that drive ovulation, and comes up mostly in research on women with PCOS or irregular ovulation.

The highest-quality evidence is a Cochrane review of 13 trials in 1,472 women with PCOS (most undergoing IVF or ICSI, not natural conception), which couldn't determine whether myo-inositol improves the chances of having a baby, rating the evidence as low to very low quality. A more recent review reached a similar conclusion, and current international PCOS guidelines treat inositol as an experimental therapy for infertility given the insufficient evidence, not a first-line one. Research has generally used gram-level doses (2 to 4 g per day), but no optimal fertility dose or ratio has been established, including the specific inositol ratios sometimes marketed for PCOS. Myo-inositol has also been studied during pregnancy without an obvious safety signal, but whether to continue after conception is worth discussing with your healthcare provider rather than assuming it's automatically fine.

Male fertility matters too

Sperm concentration, motility, morphology and DNA integrity all contribute to reproductive potential, and nutrition has been studied here too, particularly antioxidants.

A 2022 Cochrane review of 90 trials in over 10,300 subfertile men found antioxidant supplementation (including CoQ10, selenium and zinc) may raise live birth and clinical pregnancy rates, from roughly 16 in 100 without antioxidants to 17-27 in 100 with them. When lower-quality studies were excluded, that benefit was no longer statistically convincing, so this remains promising rather than settled.

A separate meta-analysis found selenium, zinc, omega-3 and CoQ10 each associated with improved sperm concentration, and several with better motility and morphology too. Worth flagging: these are surrogate outcomes. Better numbers on a semen analysis don't automatically mean a higher chance of a live birth.

There's no single evidence-based "male fertility stack." Trials have used a wide range of doses, combinations and durations, and neither the Cochrane review nor the sperm-quality meta-analysis establishes one regimen as standard. Doses used in these studies should be treated as research protocols rather than a standard prescription, worth discussing with a doctor rather than assembling from a blog post. It's also worth knowing that a pregnancy-specific prenatal isn't formulated around male nutrient requirements, so his supplementation is worth considering separately rather than simply sharing hers.

Beyond supplements

Smoking, heavy alcohol use, and weight-related health conditions all have real, well-established fertility evidence behind them, more consistently than most individual supplements discussed above. Sleep and general activity likely matter too, though the evidence there is less clean-cut. None of this replaces attention to nutrition, but it sits alongside it, and for some people it matters more.

Where this leaves you

Folate has the strongest, clearest preconception recommendation of anything in this article, and it's the one piece we'd call close to non-negotiable. Omega-3, selenium, zinc and vitamin D are already in our Prenatal Core, so you likely don't need to add anything separately just because you've seen them mentioned in fertility research, though none of these has one universally "correct" fertility dose established in the literature.

CoQ10 and myo-inositol are two supplements you'll likely encounter in fertility content, but neither is a universal requirement, the strongest evidence for both comes from specific populations, IVF patients and women with PCOS respectively, not general natural conception. Whether either belongs in your plan depends on your individual circumstances, and is worth a conversation with a doctor rather than a decision made from a blog post.

And if conception is taking longer than you'd hoped, that's common, not a failure. Fertility specialists, IVF, egg freezing and donor options exist precisely for this, and getting a professional opinion, rather than researching your way to certainty, tends to open up more paths than waiting does.

This article is for general educational purposes and isn't medical advice. Fertility, nutrient needs and safe supplement doses vary from person to person, especially if you have an existing health condition, are taking other medication, or are already pregnant. Please consult a doctor, gynaecologist or fertility specialist before starting any new supplement or treatment.

Sources

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