What Are the Common Side Effects of Prenatal Vitamins?

Pregnant woman holding a pill and a glass of water

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Most people who are or are trying to become pregnant would do anything to increase their chances of having a healthy baby and pregnancy. As it happens, there are pills you can pop for precisely this purpose: prenatal vitamins. 

Healthcare providers typically recommend them for people who are trying to conceive, are already pregnant, or are breastfeeding. They ensure these patients get ample amounts of the vitamins and minerals that are essential to pregnancy and the postpartum period. 

After all, pregnancy and nursing take a lot out of the body, says Georgia-based board-certified OB/GYN Renita White, MD. That’s why it’s important to begin taking prenatal vitamins before you get a positive pregnancy test, when possible.

While supplements aren’t FDA-regulated or standardized, most prenatal vitamins look a lot like other types of vitamins with extra folic acid, iron, and iodine. “From a population perspective, we can’t ensure pregnant women are consuming these nutrients through food in appropriate doses,” explains Amy M. Valent, DO, assistant professor of obstetrics and gynecology at Oregon Health and Science University. What’s more, food aversions can make it even more difficult for pregnant people to get enough micronutrients from their diets.

While prenatal vitamins can bridge nutritional gaps to prevent deficiencies and reduce the risk of delivering a baby prematurely or with low birth weight or size for their gestational age, they can cause some adverse effects in some cases. The thing is, symptoms like constipation, nausea, and bloating can also result from the pregnancy itself, so it can be difficult to pinpoint whether the supplements are responsible, says Dr. White. Luckily, in cases where prenatal vitamins are in fact the culprit, there are ways to mitigate discomfort.

Read on to find out more about what to expect when taking prenatal vitamins and how to minimize side effects. 

Common Side Effects of Prenatal Vitamins 

Even among the most seasoned medical professionals, it’s not always easy to distinguish between pregnancy symptoms and prenatal vitamin side effects. So how can you tell which is to blame? “It’s a million dollar question,” says Dr. Valent. “As pregnancy progresses, there are no two hours that are the same. Even if you stop taking your prenatal vitamin and your symptoms go away, there’s no saying whether that’s because of your pills or your pregnancy.” 

Nevertheless, prenatal vitamins can contribute to the following side effects in some cases.

Constipation

Also a common side effect of pregnancy, constipation can be caused by the iron in prenatal vitamins. The true cause here isn’t known, says Dr. Valent, who notes that taking iron supplements with vitamin-C-containing citrus can improve absorption and potentially mitigate this symptom. 

Nausea

Dr. Valent chalks nausea up to pill size and/or scent. After all, the additional micronutrients in prenatal vitamins tend to make the pills bigger, which could trigger nausea during an attempt to swallow. Some pills also carry a triggering smell or are manufactured with preservatives that exacerbate this symptom, she says, noting that the micronutrients themselves aren’t typically at fault. 

Bloating

While it’s hard to say whether reports of bloating are due to pregnancy or prenatal vitamins, some pregnant individuals are particularly sensitive to the omega-3 fatty acid docosahexaenoic acid (DHA) or fish oil sometimes found in prenatal vitamins, Dr. Valent says. 

Gassiness

Another possible side effect of the DHA in fish oil that can show up in prenatal vitamins is gassiness. This can be caused by what you ate before or with your prenatal vitamins, Dr. Valent says.

Allergic Reaction

Belly discomfort, nausea, or vomiting after taking a prenatal supplement can be a sneaky sign you’re allergic to something in the supplement, according to Dr. White. While it’s uncommon to react to micronutrients, the culprit could be an ingredient used to make the capsule or tablet, an issue that’s not unique to prenatal vitamins. 

Dry or Itchy Skin

Found in fruit, eggs, milk, carrots, sweet potatoes, and cantaloupe, “It’s easy to consume vitamin A through food, so you may not need as much through supplementation,” Dr. Valent says. Dry, itchy skin patches could be a sign you’re getting too much.

Bruising

If you notice that you bruise more easily since starting prenatal vitamins, it may not be in your head. Depending on the way your body processes vitamin E or vitamin K, which are involved in the body’s blood clot response, you may indeed be more prone to bruising, Dr. Valente says.

How to Manage Side Effects 

The easiest way to sidestep prenatal vitamin side effects is to try a different brand. “Not every prenatal vitamin is the same,” Dr. Valent says. 

If that doesn’t cut it, change up when you take the vitamin: “It might go down better in the afternoon than in the morning when you’re more reactionary, or after a meal that contains good fats or citrus, which help optimize the absorption of some nutrients,” she says.  

You can also halve your pills and take one half in the morning and one half in the evening, or—with your healthcare provider's approval—try taking the pills every other day, Dr. White suggests. (This last option may not be appropriate for people carrying twins, who might need more of certain nutrients such as folic acid and iron.)

But at the end of the day, if you simply find it challenging to swallow larger pills, you can always take individuals, Dr. Valent says. Just talk to your healthcare provider about which ones you need in addition to folic acid. 

When to See a Healthcare Provider

Disruptive symptoms like nausea, vomiting, constipation, and skin changes that persist after changing vitamin brands may warrant a conversation with your provider, according to Dr. White. “It could indicate a problem that has nothing to do with the vitamin,” she says, adding that prenatal vitamin side effects should be mild and short-lived. 

A Word From Verywell

People who are trying to become pregnant, are already pregnant, or are breastfeeding should take prenatal vitamins—ideally beginning three months before the first attempt to conceive, through pregnancy, and for the duration of breastfeeding. While side effects like nausea, bloating, and skin changes are possible, there’s no reason to grin and bear them. Switching brands is the easiest way to suss out whether your symptoms are related to your vitamins or directly linked to your pregnancy.

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