The conversation about what to eat during pregnancy usually happens at the first prenatal appointment — which is typically around 8 to 10 weeks in. But neural tube formation is complete by week 4. The window where nutrition matters most happens before most women know they're expecting, let alone talking to a doctor about it.
Starting a preconception nutrition focus at least three months before trying gives time to build stores of the nutrients that matter most and to identify and correct any deficiencies. This isn't about eating a specific diet. It's about knowing which nutrients have the clearest evidence and actually prioritizing them.
The folate question: folic acid or methylfolate?
Folate (vitamin B9) is the nutrient with the most compelling preconception evidence. ACOG recommends starting supplementation at least one month before trying to conceive. Folic acid — the synthetic form — is the standard recommendation and has decades of data on neural tube defect prevention.
The case for methylfolate comes from MTHFR genetics. Around 40% of people carry a common variant in the MTHFR gene that reduces their ability to convert folic acid to its active form (5-MTHF). For these women, folic acid supplementation may not raise active folate levels as effectively. Methylfolate bypasses this conversion step entirely. Testing for MTHFR variants is available and worth discussing with your OB-GYN if you have a personal or family history of neural tube defects, pregnancy loss, or if you've been on hormonal contraception long-term (which depletes folate). For most women without known MTHFR variants, standard folic acid at the ACOG-recommended intake level is effective.
Choline is the most underappreciated preconception nutrient. A 2018 Cornell study found that maternal choline intake during pregnancy significantly influences fetal brain development and memory function — effects that persisted in children at 7 years of age. Yet 92% of pregnant women in the US don't reach the adequate intake for choline. Good dietary sources include eggs (particularly the yolk, which contains the most choline per food source), beef liver, and salmon. The conversation about prenatal nutrition needs to include choline alongside folate. Most standard prenatal vitamins don't contain enough.
The other nutrients that matter most
Folate gets most of the attention, but several other nutrients have meaningful evidence for preconception and early pregnancy support. Getting tested before you start trying gives you time to address gaps before they matter.
Iron: Iron deficiency affects roughly 30% of women of reproductive age. Starting pregnancy depleted means catching up from behind — which is harder to do in the first trimester when nausea may limit intake. Having ferritin checked before trying gives you a baseline and time to address it. Your OB-GYN can advise on appropriate iron intake based on your levels.
Iodine: Critical for fetal thyroid development and neurological function. Iodine deficiency is the most common preventable cause of intellectual disability worldwide. Many women don't get enough, especially those avoiding iodized salt or dairy. Most prenatal vitamins include iodine, but check the label — not all do.
Vitamin D: Low vitamin D before and during pregnancy is associated with gestational diabetes, preeclampsia, and lower birth weight. A baseline test before trying is worthwhile given how common deficiency is. A prenatal vitamin with vitamin D is a reasonable start; getting tested tells you whether more is needed.
Omega-3 DHA: DHA is a structural component of the fetal brain and retina. Most women don't get enough from diet alone. Algae-based DHA supplements are an evidence-based option for women who don't eat fatty fish regularly — they're vegan-friendly and the direct source (fish get their DHA from algae).
Choline: Most prenatal vitamins don't contain enough. Eggs — especially the yolks — are the easiest way to increase intake through food. Two whole eggs a day contributes meaningfully. This is one where food genuinely matters more than supplements for most women.
CoQ10: Small studies suggest a role in egg quality, particularly in women over 35. The evidence is early and hasn't yet come from large RCTs — so it's in the "plausible but not proven" category. Not unreasonable to discuss with your OB-GYN if you're 35 or older, but not a priority above the nutrients above.
What to bring to your preconception appointment
- "I'd like to get my iron, vitamin D, and thyroid levels checked before we start trying" — baseline labs give you time to act on anything low
- "Do I need to test for MTHFR, or is standard folic acid the right choice for me?" — especially relevant if you have a family history of neural tube defects or pregnancy loss
- "Which prenatal vitamin do you recommend, and does it include iodine and choline?" — many don't; this is worth checking
- "I've been on hormonal contraception for [X years] — does that affect my nutrient status going in?" — OCP depletes folate, B12, zinc, and magnesium over time
A note from our medical advisors
A preconception appointment is underused and undervalued. Most women schedule their first OB visit after a positive pregnancy test. Coming in before you start trying — ideally 3 to 6 months ahead — gives your provider time to address thyroid conditions, run baseline labs, review medications for pregnancy safety, and discuss supplementation properly. It's worth asking for one specifically. Many practices don't offer them routinely but will schedule one if you ask.
References
- ACOG Committee Opinion #762. Prepregnancy Counseling. Obstet Gynecol. 2019;133(1):e78–e89. PubMed 30575679
- Caudill MA, et al. Maternal choline supplementation during the third trimester of pregnancy improves infant information processing speed. FASEB J. 2018;32(4):2172–2180. PubMed 29217669
- Smithells RW, et al. Possible prevention of neural tube defects by periconceptional vitamin supplementation. Lancet. 1980;1(8164):339–340. PubMed 6101792
- Dror DK, Allen LH. Iodine in Human Milk: A Systematic Review. Adv Nutr. 2018;9:347S–357S. PubMed 29767698
- Greenberg JA, et al. Folic acid supplementation and pregnancy: more than just neural tube defect prevention. Rev Obstet Gynecol. 2011;4(2):52–59. PubMed 22102928