Your very first pregnancy appointment with a doctor or midwife will probably include checking your vitals, having an ultrasound to help determine the due date of your baby, and a lengthy discussion on the do’s and don’ts of pregnancy. One recommendation almost every provider will give you is to start taking a prenatal vitamin (if you weren’t taking one already!). But are all prenatal vitamins created equal? Can you choose any prenatal off the shelf at your local pharmacy and expect to receive the same benefits?
And—even more importantly—why should you take a prenatal vitamin in the first place?
Why prenatal vitamins are recommended during pregnancy
The most basic reason pretty much every healthcare professional recommends you take a prenatal vitamin is because your nutrient needs during pregnancy dramatically increase, and it can sometimes be difficult to meet those needs from diet alone. One of the most researched and discussed nutritional deficiencies during pregnancy is folate or folic acid, which is crucial in preventing neural tube defects, heart defects, cleft palate, and cleft lip.
It’s actually vital to take folate before you’re pregnant, as the defects that can be caused by a folate deficiency occur within the first few weeks of pregnancy (often before you even know for sure that you’re pregnant). Because of this, folate is one of the most vital nutrients during pregnancy and is important to take pre-conception as well. Folate (also known as vitamin B9) is naturally found in foods like liver, egg yolks, legumes, and leafy greens, but it is typically found in prenatal vitamins in its synthetic form, folic acid.
A note on folic acid versus methylated folate
One of the more confusing distinctions between different prenatal vitamins is whether they contain the synthetic folic acid or another form of folate known as L-methylfolate. Folic acid is not just commonly found in prenatal vitamins, it’s also added to commercially-made fortified grain products like cereals, bread, tortillas, flour, and pasta. The majority of prenatal vitamins on the market use folic acid, but a growing number of brands are making the switch to methylated folate (which will probably appear as L-methylfolate on a supplement label).
The main difference between these two forms of folate is that while both need to undergo a conversion process to make them bioavailable for our bodies, folic acid is more difficult to convert if you have a genetic mutation called the MTHFR mutation [1].
MTHFR mutations occur in around 60-70% of the general population, and essentially make it so your body has difficulty processing and utilizing folate. If you have this genetic mutation, you might have difficulty absorbing much of the folic acid you consume in either fortified grain products or in a prenatal vitamin. Luckily, this is bypassed by the usage of L-methylfolate instead [2].
Is it a problem to have large quantities of unmetabolized folic acid in the body?
Those with the MTHFR mutation risk having unmetabolized folic acid if they consume folic acid in large quantities either through supplementation or fortified foods [3]. Unmetabolized folic acid is quite common in Americans (largely due to the number of commercial foods that have folic acid added to them) [4]. To date, research is conflicting regarding whether high levels of unmetabolized folic acid in the body have adverse effects such as increased cancer risk and/or poorer metabolic health [5].
While folic acid is much more studied than L-methylfolate to date, there are no known downsides to using L-methylfolate rather than folic acid even if you do not have the MTHFR mutation. A 2023 literature review found that supplementation of the more bioavailable L-methylfolate may be a “better alternative” to supplementing with synthetic folic acid [6]. Of note, proper absorption of L-methylfolate requires adequate amounts of Vitamin B12. For this reason, some L-methylfolate products include Vitamin B12.
What nutrients should your prenatal vitamin contain?
All of that being said, when you are shopping for a prenatal vitamin, consider first what form of folate is being used. Methylated folate will most likely appear as L-methylfolate but it could also be called 5-methyltetrahydrofolate. Vitamins that use this form of folate may be more effective (especially if you’re in the majority camp of people with the MTHFR mutation) than folic acid.
Besides folate, you’ll also want to look for the other heavy hitters—nutrients that are both important in pregnancy and in which pregnant women are commonly deficient. These include vitamin D, vitamin E, iron, zinc, and magnesium (see Real Food for Pregnancy, pg. 95). Other important nutrients include calcium, vitamin C, vitamin A, B vitamins (including vitamin B6, which is helpful for morning sickness!), zinc, and iodine. This 2022 literature review sums up the nutrient deficiencies associated with the most common pregnancy complications [7].
Should your prenatal contain iron?
Another important nutrient for pregnancy is iron, as anemia (iron deficiency) is quite common in pregnancy due to the fact that a pregnant woman’s body has double the volume of blood that it normally has. This makes it difficult to make enough red blood cells without an increased amount of iron, causing anemia. That being said, iron supplements (whether taken on their own or within a prenatal) can oftentimes cause nausea or GI discomfort as a side effect, which is the last thing you want if you’re already struggling with morning sickness. Some prenatal brands do not include iron due to consumer demand for a supplement that does not make you nauseous, while others don’t include iron because supplementation needs may vary significantly from one woman to the next.
Luckily, most medical providers will routinely check iron levels throughout pregnancy so you know if you are becoming anemic or not. Personally, I take a prenatal without iron because I do experience nausea when I take an iron supplement, but I make sure my doctor knows this and checks my iron a few times throughout pregnancy. If my iron levels are low, I increase natural sources of iron in my diet like red meat, dark leafy greens, and cooking in a cast iron pan.
Finding a quality prenatal
Another factor to consider when shopping for a prenatal is that while all of them will list the Percent Daily Value for each nutrient and oftentimes include “100% daily value” for each vitamin and mineral, the recommended dietary allowance (RDA) might not actually be enough for optimal nutrition. According to prenatal dietician and author of Real Food for Pregnancy, Lily Nichols:
“Some prenatal vitamins are less comprehensive than they seem, either lacking certain vitamins entirely or not including adequate amounts. It’s important to keep in mind that most recommended dietary allowance (RDAs) for nutrients were set using data from adult men and adjusted via complex estimates to meet the needs of pregnancy. Also, they are set as a level to prevent severe deficiency, but not necessarily at a level for optimal nutrition.” (Real Food for Pregnancy, pg. 96).
Prenatal vitamins aren’t a one-stop shop for nutritional health during pregnancy
Due to this, Nichols says pregnant women should think less of prenatal vitamins as their one-stop shop to ensure nutritional health during pregnancy, and more as an insurance policy to cover any gaps in their diet. She also cites a number of studies that show how the current RDA during pregnancy might be drastically lower than what it should be for certain nutrients—including vitamin B12, vitamin B6, and vitamin D [9][10][11]. There are also other nutrients like choline that are often absent altogether from prenatal vitamins, largely because they have only been studied in the past twenty years or so.
Because many prenatal vitamins on the market are largely insufficient, Nichols says, we need to use a critical eye when choosing a prenatal. Luckily, she offers a free guide to prenatal brands that are comprehensive in their nutrient choices—including the most bioavailable forms (such as L-methylfolate instead of folic acid) of vitamins and minerals and have evidence-based doses of the nutrients they include. Some of the brands she recommends include Full Well, Seeking Health, Thorne, and Smarty Pants gummies (although she only recommends gummies for women whose nausea prevents them from taking regular prenatal vitamins). Vita Prenatal Formula Capsules, developed with nutritionist Marilyn Shannon (author of Fertility, Cycles, & Nutrition), are another good option.
The bottom line on choosing a quality prenatal vitamin
While the sheer number of prenatal vitamins on the market might seem daunting, some are certainly better than others. But no matter which prenatal you choose, it’s important to view it as a means of filling the nutritional gaps you have, rather than an end-all-be-all to pregnancy health. Having good nutrition alongside your prenatal vitamin is the best way to set yourself up for success during pregnancy.
