Prenatal vitamins help ensure that your baby develops healthy. By delivering key nutrients needed for early development, prenatal vitamins can reduce the risk of birth defects and improve your baby’s ability to grow and thrive.
Want to know more about the specific benefits of prenatal vitamins? Below, our research team has laid out their findings on why prenatal vitamins work, including some surprising findings, like why you should start taking them before you’re even pregnant.
Prenatal vitamin benefits
1. Prenatal vitamins are formulated based on science
Prenatal vitamins are special supplements designed with the intent of helping your soon-to-be-born baby to be as healthy as possible.
The focus with prenatal vitamins is to provide nutrients that have been scientifically connected with better fetal development in large-scale randomized controlled trials–the gold standard in medical research.
In an ideal world, your prenatal supplement is only one facet of ensuring your baby is as healthy as possible—staying healthy during pregnancy in other ways, like getting exercise and eating a well-balanced diet, is part of the equation too.
2. Prenatal vitamins should be taken before you get pregnant
Given the name, you might think you should start taking prenatal vitamins once you know you are pregnant. However, this is a mistake! Many critical developmental steps that rely on proper nutrition happen very early on during pregnancy—in the first few weeks.
Once you start considering having a baby, you should already start taking a prenatal vitamin. The good news is that there is no real downside to taking a quality prenatal vitamin—they provide pretty much the same benefits as a regular women’s multivitamin if you don’t get pregnant.
3. Nutrition during pregnancy determines the health of your baby
As the science of nutrition took off during the 20th century, scientists began to realize how important proper nutrition is during pregnancy.
As a baby develops, it is very vulnerable to nutritional deficiencies, and a deficit of a few critical vitamins and minerals are known to cause problems.
4. Vitamins B9 and B12 are some of the most important nutrients for fetal development
There is a substantial body of science that connects low levels of vitamin B9 (folate) and vitamin B12 (cobalamin) with an increased risk of neural tube defects, a birth defect that affects the spinal cord as it develops.
According to a scientific article published in 1993 by P.N. Kierke and other researchers at the Health Research Board in Dublin, Ireland, blood levels of both folate and vitamin B12 are directly and independently linked to prevention of neural tube defects in infants (1).
They showed that vitamin levels in the blood were strongly correlated with a reduced risk of this type of birth defect in over 50,000 pregnant women.
Moreover, many of the women whose folate and B12 intakes were up to normal dietary standards still had low levels of folate and B12 in their blood, which caused calls for revisions to dietary intake standards.
This research, and other papers like it, spurred the United States Food and Drug Administration to create new standards for fortifying processed foods with folic acid (another form of folate) and vitamin B12 in order to prevent neural tube defects.
As a result, the average blood folate levels in pregnant women more than doubled, but some women still have low levels of folate (2).
5. Iron is another critical nutrient, especially in the second and third trimester
During pregnancy, your iron needs are also quite high, since you are producing blood for two people instead of one. According to one study, the total added iron needs during pregnancy sum to over 1000 mg (3).
Much of this required iron comes during the second and third trimester, and many women do not have enough bodily iron reserves to support this demand for iron.
Bothwell writes that, for many women, especially those with a subpar diet, fortification of their food or supplementation of their diet with an iron supplement. For this reason, almost all prenatal vitamins include iron as a part of their formulation.
The format of the iron supplied varies from product to product—though many different types of iron are absorbable, amino acid chelates tend to be better-tolerated.
6. Your prenatal vitamin should not have too much calcium, since it inhibits iron absorption
This phenomenon is well-described in nutritional research (4).
The interaction is strong enough that most high-quality prenatal vitamins have barely any calcium in them at all. You should check your prenatal vitamin’s label to make sure there isn’t too much calcium in it.
However, it’s also important to get calcium during pregnancy too. The best strategy to avoid problems is to take a calcium supplement or eat calcium-rich food at least a few hours apart from taking your prenatal vitamin.
7. A prenatal vitamin with omega 3 fatty acids can promote cognitive development
There is a wide base of scientific evidence indicating that omega 3 fatty acids, such as those found in fish oil or vegan omega 3 supplements, are associated with brain health, but emerging evidence is indicating that it’s at least as important for brain development during pregnancy.
For example, one review study by doctors at Harvard Medical School showed that omega-3 fatty acids plays a critical role in brain and eye development during pregnancy (5).
Further, the authors suggest that women have a higher need for omega-3 fatty acids during pregnancy compared women who are not pregnant.
Women who are pregnant need to be conscious of the content of mercury in fish: more than two servings per week of fish could expose your baby to unsafe levels of mercury, which has a decidedly negative effect on brain development.
As such, supplementation is really the only game in town when it comes to safely getting enough omega 3 fatty acids in your diet when you are pregnant.
8. Omega 3 fatty acids might help prevent peripartum and postpartum depression
Omega 3 fatty acids have been researched quite a bit in their own right for treating and preventing depression (often performing as well as prescription antidepressants), but it wasn’t until 2008 that randomized clinical trials directly examined omega-3s for the prevention and treatment of depression in pregnant women (6).
Pregnancy itself increases the risk of psychological distress and mental health problems, so if a prenatal vitamin that delivers omega-3s could reduce this risk, that would be an even better reason to take them.
In the experiment, conducted by researchers in China, 62% of the women taking the omega-3 containing supplement responded to treatment, compared to only 27% of the group taking the placebo supplement. These results, though from a small study, make taking a prenatal vitamin that provides omega-3 fatty acids sound like an even better idea.
Prenatal vitamin side effects
A good prenatal vitamin should not have any significant side effects. Since they are specifically designed with safety in mind, a quality prenatal supplement should not have any major side effects.
If the iron content in your prenatal vitamin causes stomach problems, try one with a different form of iron. Some women find that consuming high levels of iron (especially in inorganic forms) can cause mild gastrointestinal problems (7).
Still, it’s important to keep your body’s iron stores high during pregnancy, so if this occurs, you can try switching to a prenatal vitamin that supplies iron in a chelated form, or spreading the dosage out throughout the day.
Prenatal vitamin dosage
A good prenatal vitamin takes care of dosage for you. Fortunately, the recommended dosage is taken care of by the supplement designers in a quality prenatal vitamin. You should examine the nutrition facts label to check the levels of four key ingredients, though: vitamin B9 (folate/folic acid), vitamin B12, iron, and calcium.
Make sure your prenatal vitamin has the right amount of B9, B12, and iron. The Mayo Clinic recommends that you consume at least 400 micrograms (mcg) of folate per day before and during pregnancy, and vitamin B12 and iron should be supplied in amounts close to or exceeding 100% of your daily needs (8).
Don’t overdo it with calcium. The calcium content in your prenatal vitamin should be limited, otherwise you’ll be interfering with your iron absorption.
Prenatal vitamin benefits FAQ
Q: When should you take a prenatal vitamin?
A: Experts recommend that you start taking a prenatal vitamin as soon as you begin trying to get pregnant. That’s because of the lag time between when you conceive and when you typically find out that you’re actually pregnant.
Of course, that’s not always possible, so if you do find out that you are pregnant and aren’t taking a prenatal vitamin yet, starting sooner rather than later is a good idea.
Many important fetal milestones in development happen in the first two trimesters, so making sure you have the necessary vitamins and minerals to support this development is very important.
Q: Is it good to take a prenatal vitamin before you get pregnant?
A: Yes, in fact that is precisely what experts at institutions such as the Mayo Clinic recommend (9).
Because of the lag between getting pregnant and finding out that you are pregnant, it’s better to already have the proper levels of vitamins and minerals in your body to support a pregnancy when you conceive, versus waiting several weeks before you find out you’re pregnant to start taking a prenatal vitamin.
Incidentally, it’s also a good idea to keep taking a prenatal vitamin after you give birth, for at long as you are breastfeeding, so that your newborn baby gets the same nutrients via breastmilk.
Q: What happens if you miss a prenatal vitamin?
A: If you miss just one dose, it’s not a big deal. Maintaining high levels of vitamins like folic acid and minerals like iron, as well as other nutrients like omega-3 fatty acids, is more about consistent intake versus taking a supplement exactly every 24 hours.
The one potential exception to this is folic acid; it’s both absorbed and excreted relatively rapidly by your body, so if you forget to take a prenatal vitamin in the morning, it’s good to take it when you remember in the afternoon, then return to your usual routine the next day.
That aside, missing a dose here or there is not a huge deal—keep in mind that the clinical research that demonstrated the efficacy of folate supplementation was done on women in the real world, so many of them no doubt forgot to take a dose here and there.
Even in the face of occasional forgetfulness, the results still resoundingly support the benefits of the folate for pregnant women.
Q: What are the most important ingredients in a prenatal vitamin?
A: The most important ingredients are the B vitamins, particularly vitamins B12 and B9. These are the ones most strongly associated with preventing birth defects.
However, you also shouldn’t neglect vitamin D, iron, and omega-3 fatty acids, since there’s plenty of research supporting the notion that these ingredients support both your health and your baby’s health too.
Related: Our best prenatal vitamin picks
Every woman who’s nursing, pregnant, or trying to get pregnant should be on a high-quality prenatal vitamin. These supplements deliver critical vitamins and minerals for fetal development, including vitamin B9, vitamin B12, and iron, all of which are essential for proper development.
Solid scientific research has repeatedly shown that prenatal vitamins reduce the risk of birth defects and improve infant growth and development, so it’s well worth the effort to do some research and find the best prenatal vitamin for you.