This is day one. Before anything else, before tracking, before timing — a prenatal vitamin. And specifically one with methylated folate (5-MTHF), not just folic acid.

Why methylated? Roughly 30–40% of people carry MTHFR variants that reduce their ability to convert folic acid into its usable form. Methylfolate bypasses that conversion entirely. Most REs have shifted to recommending it as standard because there's no downside — it works for everyone regardless of MTHFR status.

Your prenatal should also include choline (at least 150 mg, ideally 300+ mg). ACOG added choline to prenatal recommendations, yet most prenatals still don't include an adequate amount. The research on choline and neural tube development is nearly as strong as folate.

If your prenatal is the foundation, CoQ10 is the single most important add-on. It supports mitochondrial function in eggs, and mitochondrial energy is the primary driver of egg quality and successful cell division after fertilization.

A 2018 Cochrane-style review and multiple randomized controlled trials have shown that CoQ10 supplementation improves oocyte quality, fertilization rates, and embryo quality — particularly in women over 35. One landmark study in Fertility and Sterility found that CoQ10 supplementation before IVF significantly improved ovarian response and embryo quality.

Form matters enormously here. Ubiquinol is the reduced (active) form of CoQ10. Ubiquinone is the oxidized form your body must convert. After about age 30, that conversion becomes less efficient. Every RE who recommends CoQ10 specifies ubiquinol for patients over 30.

Your RE will order a 25-hydroxyvitamin D blood test at your first visit. Not because they're being thorough — because vitamin D deficiency is staggeringly common (40–60% of reproductive-age women) and the data on fertility outcomes is substantial.

A meta-analysis in Human Reproduction Update found that vitamin D-sufficient women had significantly higher clinical pregnancy rates and live birth rates in both natural conception and IVF cycles compared to deficient women. The mechanism involves vitamin D receptors in the ovaries, endometrium, and placenta.

Most REs target a blood level of 40–60 ng/mL. If you're below 30 (most people are), expect a recommendation of 4,000–5,000 IU daily until levels normalize.

DHA is a structural fat in the brain and nervous system. Your baby will need enormous amounts of it, and they'll take it from you. Starting omega-3 supplementation before conception builds your stores for when demand skyrockets.

Beyond fetal development, omega-3s have anti-inflammatory properties that support implantation and reduce the risk of preeclampsia. A 2018 Cochrane review found that omega-3 supplementation reduced the risk of preterm birth by 11%.

Quality matters more with fish oil than almost any other supplement. Rancid or poorly purified fish oil can do more harm than good. Look for third-party testing (IFOS certification), molecular distillation, and triglyceride form.

DHEA is the most controversial supplement in fertility medicine, and the most important one to never take without your RE's guidance.

DHEA is a precursor hormone that your body converts into testosterone and estrogen. In women over 35 with diminished ovarian reserve (DOR), supplementing with DHEA for 6–16 weeks before IVF has been shown to improve follicle development, oocyte yield, and embryo quality in several studies — most notably from the Center for Human Reproduction in New York.

But DHEA is hormonal. In women with PCOS or normal ovarian reserve, it can cause acne, hair growth, and hormonal disruption. This is not a self-prescribe supplement. It's one your RE monitors with blood work.

If you have PCOS, your RE will almost certainly recommend inositol. It's one of the best-studied supplements for PCOS-related fertility issues, with evidence showing improvements in ovulation, insulin sensitivity, egg quality, and hormonal balance.

The 40:1 ratio of myo-inositol to D-chiro-inositol mirrors your body's natural ratio and has the strongest clinical support. A 2017 meta-analysis in Gynecological Endocrinology found that myo-inositol significantly improved ovulation rates and pregnancy rates in PCOS patients.

Even in non-PCOS patients, some REs are starting to recommend myo-inositol before IVF cycles based on emerging data showing improved oocyte and embryo quality.

NAC is a precursor to glutathione, your body's most powerful antioxidant. In fertility, it serves double duty: reducing oxidative stress on eggs and improving insulin sensitivity in PCOS.

A meta-analysis of 22 studies (2,515 women) found that NAC combined with Clomid produced a 49% ovulation rate compared to 1.3% for placebo alone in women with Clomid-resistant PCOS. That's not a supplement effect — that's a pharmaceutical-level result.

REs also sometimes recommend NAC for endometriosis-related inflammation and for improving cervical mucus quality.

3+ months before TTC or treatment: Start prenatal, CoQ10, vitamin D, omega-3. Egg maturation takes roughly 90 days from recruitment to ovulation. You're supporting eggs that will be ovulated in 3 months, not this month.

6–16 weeks before IVF (if applicable): Start DHEA (if prescribed), increase CoQ10 dose, add melatonin.

At positive pregnancy test: Continue prenatal, omega-3, vitamin D. Stop CoQ10 (no established safety data in pregnancy at therapeutic doses). Stop DHEA immediately. Stop melatonin. Consult RE about NAC and inositol continuation.

Male partner: Start everything 90+ days before you need improved sperm. If you're doing IVF in September, he starts supplements in June.