Prenatal Vitamins: Benefits, Side Effects & How To Choose One For You

Photo: Vera Lair

Prenatal vitamins are often considered an essential step for a woman trying to conceive. Just a simple internet search of “prenatal vitamins” or “prenatal vitamin benefits” can produce some confusing and contradictory information about prenatal vitamins, which can be entirely overwhelming for a newly pregnant woman. As a naturopathic doctor, registered dietitian, and mother of two who has been there—I will share some information in this article to help guide you in choosing the right prenatal for you. As always, though, I recommend talking to your health care professional about customizing your prenatal for you.

Interestingly, prenatal vitamins date back to the early 1970s, when vitamin companies started adding folic acid to their multivitamins and then marketing them specifically to pregnant women. Research on the effects of folate deficiency and birth defects predates that with research published as early as the 1950s.

In a nutshell, a prenatal vitamin is a multivitamin tailored to the specific needs of pregnancy. Throughout pregnancy the body requires greater amounts of certain nutrients such as folate, calcium, DHA, and iron. A prenatal vitamin is customized to support a pregnancy by meeting these increased nutritional needs through supplementation.

Do I need to take a prenatal vitamin?

The jury is out on whether prenatal vitamins are necessary for everybody. Many professionals believe that if you eat a healthy diet and make sure to meet the increased nutrient requirements during pregnancy, then taking a prenatal vitamin is not necessary. The American Congress of Obstetricians and Gynecologists has no specific guidance about whether or not pregnant women need to take a prenatal vitamin but do recommend the vitamins folic acid and calcium. However, most physicians and nutritionists, myself included, agree that taking prenatal vitamins is a good practice in supporting a healthy pregnancy and that they serve an important role in preventing birth defects.

Are there side effects or dangers of prenatal vitamins?

When taking any medication or supplement, you run the risk of side effects; prenatal vitamins are no exception to this. The most common side effects I see in my practice from prenatal vitamins are nausea and constipation. I will then work with the woman on modalities to reduce side effects including taking the prenatal with vitamin C or taking it at night before bed. Often these side effects can be reduced or managed by changing the form or brand of the prenatal or adjusting the time and setting in which the vitamin is taken—some women need to take it with food, for example.

If I want to get pregnant, when should I start taking a prenatal?

Women who are family planning should consider starting a prenatal vitamin, or at least an additional supplement of folic acid while trying to conceive. The first four weeks of pregnancy, the time when the neural tube (the spine) is forming, is the most critical for folate needs in preventing related birth defects. Six hundred (600) mcg of folic acid is recommended before conception and through the first 12 weeks of pregnancy. If you find out you are pregnant but haven’t been taking a prenatal or folic acid, the best thing to do is to start it as soon as you learn of your pregnancy.

What is the difference between a normal multivitamin and a prenatal vitamin?

With so many supplements out there, it can be difficult to distinguish the differences between a regular multivitamin, separate vitamin-specific supplements, and a prenatal vitamin. Generally, a vitamin manufacturer classifies a vitamin as a prenatal when its nutrient needs are tailored specifically to pregnancy, including but not limited to increased folic acid, calcium, vitamin D, DHA, and iron. Additionally, prenatal vitamins may have less of the fat-soluble vitamin A than standard multivitamins. Because prenatal vitamins are classified as dietary supplements, they are not subject to approval by the Food & Drug Administration (FDA).

Transparency and confirmation are important factors in choosing the right brand of vitamin. This means the vitamin should list all of its ingredients and the doses on its label. Additionally, vitamin brands that are third-party tested ensure that an independent company has tested the vitamin and that it contains what it states and does not have any undeclared ingredients.

Folic acid and prenatal vitamins.

Prenatal vitamins generally have 400 to 800 mcg of folic acid per serving. There has been ongoing controversy about which form of this vitamin should be supplemented. The two forms up for discussion are folic acid (supplemental) or folate (naturally occurring). Some research states that folic acid is better absorbed than naturally occurring folate; however, many natural practitioners believe that the synthetic form of folate (folic acid) comes with its own set of concerns. It is important to remember that more is not always better, and too much folic acid can cause unwanted side effects. The CDC recommends the upper limit for folic acid at 1,000 mg per day. Prenatal vitamins generally contain the appropriate amounts of this nutrient for the needs of pregnancy.

Vitamin D and prenatal vitamins.

Vitamin D is critical for bone development, hormone balancing, supporting the immune system, and brain health. During pregnancy, vitamin D is not only healthy for the development of the baby but can also prevent complications of pregnancy in the woman such as pre-eclampsia. Coined the “sunshine vitamin” because our bodies synthesize it from sun exposure, it is well-recognized that many women are deficient in vitamin D and even with sun exposure do not get enough for the needs of pregnancy. A prenatal vitamin should contain at minimal 600 IU of vitamin D.

Iron and prenatal vitamins.

Iron, one of the most important nutrients during pregnancy for supplying oxygen to the baby, is also one of the most symptomatic in prenatals. Iron is often blamed for the nausea and constipation side effects of prenatals, but don’t quit your prenatal just yet—there are ways around that.

Taking a prenatal with foods and drinks high in vitamin C, like orange juice, can improve the absorption of the iron and cause less constipation. I often suggest that to reduce the nausea side effect of prenatals they should be taken at night before bed. This has been successful for many of my pregnant clients. The daily recommended dose of iron during pregnancy is 27 mg, where for nonpregnant women it is 18 mg—a pretty significant difference! So it’s important to balance out the side effects of iron if your body seems to be having a hard time with the adjustment.

Calcium and prenatal vitamins.

Calcium, readily available in many foods, is an important nutrient for the development of a baby’s bones and teeth. Adequate calcium intake during pregnancy is also important for the bone health of the mother. Pregnant women need at least 1,000 mg of calcium per day.

DHA (fish oil) and prenatal vitamins.

Omega-3 fish oil, specifically docosahexaenoic acid (DHA), is an important nutrient in the development of a baby’s brain, eyes, and nervous system. This essential nutrient cannot be synthesized by the human body and therefore must be obtained from diet or supplementation. Because many women often don’t eat enough fish during pregnancy, getting this nutrient from additional supplementation is often critical. For vegan women, there are adequate DHA supplements made from algae both independently and in prenatal vitamins options. Two hundred milligrams of DHA daily is recommended during pregnancy. Not all prenatal vitamins contain DHA, so it is important to think of this nutrient when choosing your vitamin.

Should my prenatal have probiotics in it?

We are quickly learning and studying about all the benefits of a healthy gut and the importance of balancing gut bacteria for the prevention and management of certain conditions or diseases. This is true during pregnancy as well, and although we do not have much data on the benefit of probiotic use during pregnancy, there have been a number of studies that conclude probiotics are safe to use during pregnancy. As a response, many companies that make prenatals have started to add probiotics to their prenatal formulas.

Is it better to take a once-daily prenatal or one that has multiple pills?

This boils down to preference and consistency. For many women, taking multiple pills per day is not preferable, whereas for others breaking up the vitamin reduces side effects. There is no current science that states prenatal vitamins must be taken at certain times of the day. Some factors to consider are that the body has a limit for how much calcium it can absorb at once, so often once-daily vitamins actually provide less calcium than divided doses. Additionally, iron and calcium compete with each other for absorption, and since both are critical nutrients in a prenatal vitamin, some sources believe they are better when separated. Women who take pharmaceutical medications such as thyroid medications may need to take their prenatal at specific times, based on when they take their medication, usually creating a large space in between. Check with your doctor if this applies to you.

Prenatal vitamins and different stages of pregnancy.

It is true that various stages of pregnancy have different nutrition needs (such as the folic acid being most important in the first four weeks, for example); however, taking a prenatal vitamin ensures that your nutrient needs are being met throughout the pregnancy. It is not necessary to change your vitamin throughout your pregnancy if it is working well for you. It is recommended to try an alternate version if you are experiencing unwanted side effects of the vitamin such as nausea or constipation.

Prenatal vitamins for vegans and vegetarians.

There is no shortage of vegan options for prenatals today, but there are specific things to consider when choosing the vitamin. Making sure the vegan vitamin has an adequate source of DHA is an important part of choosing the right vitamin. Many vegan vitamins are also marketed as food-based prenatals—this means all the sources of nutrients in the vitamin come from food-based sources (an example of this is the folate in a vitamin sourced from broccoli). Food-based multivitamins tend to have lower calcium levels and less bioavailable folate than the conventional counterparts. However, there isn’t conclusive evidence proving vegan or food-based multivitamins are superior or inferior to more conventional prenatal vitamins.

Is there a difference between an over-the-counter (OTC) vs. prescription prenatal vitamin?

Often prescription prenatal vitamins have higher amounts of folic acid and iron than some of the OTC versions; however, this is not uniform across all prescriptions. OTC prenatal vitamins more often contain added desirable nutrients such as DHA, choline, probiotics, and B vitamins whereas the prescription versions may not include these. From a cost perspective, insurance will often fully cover the cost of prescription prenatal vitamins, making this a more financially appealing choice for many. But it’s also worth noting that without insurance, prescription vitamins can cost significantly more than over-the-counter prenatal vitamins.

Should I ever take a prenatal if I am not planning on pregnancy?

A prenatal vitamin is very much like a multivitamin and therefore is safe for most people to take. However, in the absence of pregnancy, the increased amounts of certain nutrients are unnecessary, and therefore a regular multivitamin may be a better fit. There are some exceptions: For postmenopausal women and men, the iron in the prenatal may be excessive. A common reason women take prenatals other than pregnancy is a belief that they will improve hair growth; however, research does not support this theory. Another common question clients ask about prenatals is whether their partners can prenatal—and the answer is the same as it is for a nonpregnant woman. It is most likely safe; however, there are many other options that are better suited for the nonpregnant individual than a prenatal. Always ask your doctor before changing your supplement regimen.

What is the best form of prenatal (pill, powder, chewable, liquid)?

There is not a superior form of a prenatal vitamin, but there is the right form for you. For women who have difficulty swallowing pills, a chewable or liquid is a better option. Women who experience unwanted side effects of prenatals such as nausea and constipation should try various forms to see if one is better tolerated than the others.

Are there any ingredients I should avoid in my prenatal?

Certain supplements, herbs, and vitamins in high doses are not recommended during pregnancy and should not be included in a prenatal vitamin. Vitamin A in the form of retinoids is an example of a vitamin that can be harmful to a pregnancy in high doses. Prenatal vitamins should also be without caffeine, licorice, and synthetic food colorings and dyes.


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