The standard advice among OBGYN doctors is that women who are actively trying to conceive should be taking prenatal vitamins, even if they aren’t pregnant just yet. It's also our advice to all women who are planning to try in the next few months, who are trying now, and who are preparing to freeze eggs.
This is partially because at the very early stage of pregnancy, when the crucial organs of the fetus—like the neural tube—are being formed, we usually don’t know that we are pregnant. So, to ensure that the baby has all the nutrients like folate and choline s/he needs from the very beginning of life, doctors recommend that women start taking prenatal vitamins when they start trying - ideally, at least 3 months of prenatal vitamins is recommended before pregnancy. (Then, once pregnant, women should stay on prenatal vitamins until they deliver – or even better, until they finish breastfeeding.)
But do prenatal vitamins also support your reproductive health?
Interestingly, studies have found that, yes, women who take prenatal vitamins are more likely to achieve pregnancies than those who don’t.
A large, 8-year-long follow-up study of over 18,000 women without a history of infertility found a significantly lower risk of ovulatory infertility among women who consistently took multivitamin supplements, compared to women who didn’t. While association doesn't always mean causation, the relative risk decreased with increasing adherence to the supplementation schedule, potentially suggesting a dose-dependent effect.
A 2019 review that examined existing studies on micronutrient status of women attempting pregnancy summarizes the current understanding of prenatal vitamins and fertility:
- For women who have nutrient deficiencies (and most women are low on at least some), taking prenatal vitamins before conception can restore micronutrient status to the recommended levels;
- Taking prenatals may also help manage oxidative stress, when the prenatal vitamins include antioxidants;
- Prenatal vitamins may help maintain fertility in small ways; and
- Women taking prenatal vitamins are more likely to get pregnant, and in a shorter period of time.
Vitamins with roles in female reproduction
As the review’s authors noted, well-designed studies (like prospectively randomized controlled trials, the gold standard in scientific research) investigating the combined effects of multiple nutrients is rare. Studies looking at each nutrient separately, or a combination of just a few, are more abundant. Here’s what we know about the fertility-related functions of the vitamins and minerals commonly included in prenatal vitamins.
Vitamin C and Vitamin E
Vitamin C and Vitamin E, both antioxidants, have been found to play a major role in female reproductive processes.
- Both of these vitamins may help protect eggs and sperm from DNA damages from to oxidative stress.
- For example, Vitamin E has been shown to support healthy development of embryos, while helping protect the mom's health during pregnancy.
Vitamin D
Vitamin D is one of the most actively studied micronutrients in the reproductive health context.
- Multiple studies have found that vitamin D deficiency is more common in women with PCOS than their healthy counterparts.
- While the mechanisms of action need further investigation, one 2013 review hypothesized that this may be because vitamin D directly impacts AMH production with implications on maintenance of ovarian reserve.
- Even among otherwise healthy women, those who met the daily recommended level of vitamin D and whose serum levels were adequate (over 50 nmol/L) were significantly more likely to become pregnant and deliver a healthy baby.
Experts recommend the blood Vitamin D level of at least 40 ng/mL for the preconception and prenatal periods. Levels lower than this threshold is common, especially among some ethnic groups and during winter months.
B vitamins
B vitamins have been identified as a significant contributor in the maintenance of normal ovulation, in the cohort study of 18,000+ women over 8 years, mentioned earlier.
- Another study analyzed the serum levels of vitamin B-12 and outcomes of 100 women (with 154 cycles total), and found that women in the highest quantile for vitamin B-12 levels were more than twice as likely to have a live birth, compared to women in the lowest quantile.
- How B vitamins contribute to reproductive success is still not completely understood, but one strong hypothesis relates to its ability to maintain a healthy level of homocysteine, an amino acid that negatively impacts embryo quality.
Many women are low on at least one of the B vitamins. The risk of low B vitamins is even higher if you've been using a hormonal birth control.
Folate (also a B vitamin)
Folate (also known as folic acid) appears to facilitate healthy reproductive processes in multiple ways.
- A Danish study found that folic acid supplementation was linked to higher fertility rates.
- Similar to the B vitamins, folate/folic acid is thought to help maintain a normal level of homocysteine, potentially contributing to the findings that women taking folic acid have more mature, better-quality eggs.
- Furthermore, folate supplementation has been shown to support optimal progesterone level and maintain healthy ovulation cycles.
Many prenatal vitamins use a synthetic form of folate called folic acid. We recommend ones that use active, natural form of folate called methylfolate. Here's more on the difference between folic acid vs. folate.
Bottom line on prenatal vitamins and fertility
As mentioned earlier, there aren’t quite enough well-designed studies investigating the fertility-supporting roles of multi-nutrient supplements to know for sure if prenatal vitamins can support the preconception period. One likely confounding factor: It’s possible that women who take prenatal vitamins consistently during the before they get pregnant are more informed about nutritional needs and have generally healthier habits, which may contribute to the observed benefits.
While some of the nutrients commonly included in prenatal vitamins have a significant evidence in the literature regarding their ability to facilitate conception, research is still needed to understand how they work.
Bottom line, though: Women planning to get pregnant in the near future should start taking prenatal vitamins now. That’s the recommendation of the American College of Obstetricians and Gynecologists, as well as ours. If that gives you an extra fertility support, more power to the vitamins!
Next week, we'll review the state of science on some minerals' involvement in our reproductive process. Reach out with any questions – we are with you.
