The single most important supplement when trying to conceive is folic acid, at a minimum of 400 micrograms daily, started at least one month before conception. But folic acid is just the starting point. Several other vitamins and minerals play direct roles in ovulation, egg quality, implantation, and early fetal development, and getting your levels right before pregnancy gives you a measurable advantage.
Folic Acid: The Non-Negotiable Starting Point
Folic acid prevents neural tube defects like spina bifida, which form in the first weeks of pregnancy, often before you know you’re pregnant. The American College of Obstetricians and Gynecologists recommends at least 400 micrograms daily, starting a minimum of one month before conception and continuing through the first 12 weeks. If you’ve previously had a pregnancy affected by a neural tube defect, the recommendation jumps to 4,000 micrograms (4 mg) daily, starting at least three months before conception.
You may have seen advice online that women with MTHFR gene variants should skip folic acid and take methylfolate instead. The CDC is clear on this: people with MTHFR variants can process folic acid, and folic acid is the only form of folate proven to prevent neural tube defects. Even with the most common variant (MTHFR 677 TT), blood folate levels are only about 16% lower than in people without the variant. Taking the recommended 400 micrograms daily raises blood folate levels regardless of your genotype.
Vitamin D and Pregnancy Rates
Vitamin D levels before conception are directly tied to your chances of a successful pregnancy. In a prospective study of nearly 1,200 women, those with sufficient vitamin D (at or above 30 ng/mL in a blood test) were 15% more likely to achieve a live birth and 10% more likely to achieve a clinical pregnancy compared to women with levels below that threshold. These were healthy women without an infertility diagnosis, which makes the finding especially relevant if you’re trying to conceive naturally.
About half of the women in that study had insufficient levels, which tracks with broader population data. A simple blood test from your doctor can tell you where you stand. Most prenatal vitamins contain some vitamin D, but many women need an additional supplement to reach adequate levels, particularly those with darker skin, limited sun exposure, or higher body weight.
Iron and Ovulatory Fertility
Iron from supplements and plant-based foods is associated with a significantly lower risk of ovulatory infertility, which is one of the most common causes of difficulty conceiving. Women who took iron supplements had a 40% lower risk of ovulatory infertility compared to women who didn’t, after adjusting for other factors. Interestingly, iron from meat (heme iron) showed no relationship with ovulatory fertility. The benefit came specifically from nonheme iron found in supplements, fortified cereals, beans, and leafy greens.
This doesn’t mean you need to take high-dose iron pills. The iron in a standard prenatal vitamin, combined with a diet that includes iron-rich plant foods, typically covers your bases. If you have heavy periods or a history of low ferritin, getting your levels checked before conception is worth doing, since iron stores deplete quickly during pregnancy.
Vitamin B12 and Implantation Success
B12 plays a role alongside folate in DNA synthesis and cell division, both critical during the earliest days after an embryo implants. Research on women undergoing fertility treatment found that for every 10 pg/mL increase in blood B12 (up to about 359 pg/mL), clinical pregnancy rates rose by 4%. Women with mid-range B12 levels had 83% higher odds of clinical pregnancy compared to women with low levels. One study found that women with B12 above 701 pg/mL were twice as likely to achieve a live birth as those below 439 pg/mL.
B12 deficiency is common in women who eat little or no animal products, but it can also affect meat-eaters with absorption issues. Most prenatal vitamins include B12, and a standard blood panel can reveal whether you need more.
Choline for Early Neural Development
Choline works alongside folate to support neural tube formation and brain development, and its impact begins before most women realize they’re pregnant. The recommended intake during early pregnancy is 450 mg per day, rising to 550 mg after 12 weeks. Most prenatal vitamins contain little or no choline, and most women fall short of these targets through diet alone.
Eggs are the richest common food source (one large egg has about 150 mg), followed by liver, fish, and soybeans. If your diet is low in these foods, a standalone choline supplement can fill the gap. Since neural tube closure happens around week four of pregnancy, having adequate choline levels before conception matters.
Iodine for Thyroid Function
Your thyroid controls the hormones that regulate ovulation and sustain early pregnancy, and it depends on iodine to function properly. The American Thyroid Association recommends that women planning pregnancy start taking a daily supplement with 150 micrograms of iodine, ideally three months before conception. During pregnancy, the target total intake (from food and supplements combined) rises to 250 micrograms per day.
Iodine intake has declined in many Western countries as people use less iodized salt and eat more processed foods (which typically use non-iodized salt). Dairy products, seafood, and iodized salt are the main dietary sources. Check whether your prenatal vitamin includes iodine, as not all do.
Omega-3 Fatty Acids
Omega-3 fats, specifically EPA and DHA, support the uterine environment and are essential building blocks for fetal brain and eye development. Guidelines for pregnancy recommend 650 mg of combined EPA and DHA daily, with at least 300 mg coming from DHA. These targets apply from preconception onward.
Two servings of low-mercury fatty fish per week (salmon, sardines, herring) can get you partway there. Most women still need a fish oil or algae-based supplement to close the gap, particularly for DHA. If you eat little seafood, you may need an additional 400 to 550 mg of EPA and DHA daily from supplements.
CoQ10 for Egg Quality
CoQ10 fuels the mitochondria inside your eggs, which are the tiny energy factories that power cell division after fertilization. As you age, mitochondrial function in eggs declines, and CoQ10 supplementation can partially compensate. Clinical studies have used doses of 200 mg per day (for women with normal ovarian reserve) up to 600 mg per day (for women with diminished ovarian reserve), typically started 60 to 90 days before trying to conceive or beginning a fertility treatment cycle.
At the 600 mg daily dose taken for 60 days, women with diminished ovarian reserve showed improved ovarian response. At 200 mg daily for 30 to 35 days, CoQ10 levels in follicular fluid increased, which is where the egg matures. CoQ10 is generally considered more beneficial for women over 35 or those with known egg quality concerns, though it’s increasingly included in preconception protocols for women of all ages.
Inositol for Women With PCOS
If you have polycystic ovary syndrome, inositol deserves special attention. PCOS is one of the most common causes of irregular ovulation, and inositol (a compound related to the B-vitamin family) helps improve insulin sensitivity, which in turn helps restore regular cycles. Two forms matter: myo-inositol and D-chiro-inositol.
The ratio between the two forms appears to make a significant difference. In a randomized trial of 60 women with PCOS, those taking a 3.6:1 ratio of myo-inositol to D-chiro-inositol had a 65.5% pregnancy rate and a 55.2% live birth rate, compared to 25.9% and 14.8% in the group taking the more commonly sold 40:1 ratio. The 3.6:1 ratio has also been shown to regularize menstrual cycles and improve insulin resistance. If you have PCOS, look specifically at the ratio on the label, not just whether the product contains both forms.
Timing Matters More Than You Think
The preconception window for supplementation is wider than many women realize. Starting a prenatal vitamin the month you begin trying is the minimum, but many of the nutrients above take weeks or months to reach optimal levels. Iodine and folic acid ideally start three months out. CoQ10 needs 60 to 90 days to affect egg quality, and eggs themselves take about three months to mature before ovulation. Vitamin D levels shift slowly, often requiring 8 to 12 weeks of consistent supplementation to reach sufficiency.
A good prenatal vitamin covers folic acid, iron, iodine, B12, and vitamin D as a baseline. From there, choline, omega-3s, and CoQ10 often need to be added separately, since most prenatals either exclude them or include them in doses too small to matter. If you have PCOS, adding the right inositol formulation is a targeted step with strong evidence behind it.