Wondering About Your Prenatal Vitamins and Weight Gain? Here’s Everything You Need to Know

On This Page

    If you’re pregnant, prenatal vitamins can be great for your health and the health of your developing child. But do they cause weight gain?

    What’s the argument for taking a prenatal vitamin?

    Multivitamins typically contain vitamins that may not be readily available in your diet and are therefore designed to meet the nutrient needs of the average person. Taking them may help address nutrient deficiencies.

    Prenatal vitamins are a particular class of multivitamin, and they’re specifically tailored for people who are pregnant or trying to become pregnant. They contain vitamins that are considered to be conducive to a healthy pregnancy, including folic acid, calcium, and iron.

    There is much research that’s shown that blood levels of most vitamins decrease during pregnancy, due to the fact that your body uses more of what it consumes while pregnant. In other words, your nutrient needs go up during pregnancy. Taking a prenatal vitamin can be beneficial in that it helps restore normal nutrient levels. That, in part, is why the American College of Obstetricians and Gynecologists recommends that pregnant people take a prenatal vitamin. Prenatal vitamins can help you meet your growing nutrient needs, as well as those of your developing baby.

    The prenatal weight gain myth busted

    You might have heard rumors that prenatal vitamins lead to weight gain. This turns out to be a myth. There’s no evidence to suggest that prenatal vitamins cause weight gain.

    There’s a reason people have wondered about this, though, and it’s a simple one: Weight changes are very common during pregnancy. It would be a mistake, though, to attribute pregnancy-related weight gain to your prenatal vitamin.

    Moreover, prenatal vitamins typically include iron, which can sometimes cause constipation and bloating. These symptoms can be mistakenly linked to weight gain during pregnancy.

    Weight changes during pregnancy are different for each person and are not related to whether or not you’re taking a prenatal vitamin.

    But do prenatal vitamins make you hungrier?

    No, there’s no evidence that taking prenatal vitamins will increase your feelings of hunger.

    How much weight gain should you expect during pregnancy?

    According to the American College of Obstetricians and Gynecologists, you can expect to gain an additional 11-40 pounds during a one-baby pregnancy. For twins, the range is an additional 25-62 pounds.

    Such weight gain is to be expected and is nothing to worry about. The key is to maintain a healthy weight, and the best way to determine a healthy weight for you is to talk to your doctor. Too much weight gain during pregnancy and too little weight gain during pregnancy have both been associated with adverse birth outcomes. Weight gain above these ranges can also increase the chances of having a larger baby, leading to a possible C-section delivery.

    Do prenatal vitamins make you gain weight if you’re not pregnant?

    There’s no evidence to suggest that taking prenatal vitamins when you’re not pregnant will lead to weight gain.

    You should always check your iron levels before taking a prenatal vitamin, though, since too much iron can be toxic. Talk to your doctor before supplementing.

    What are other reasons for weight gain during pregnancy?

    If weight gain during pregnancy isn’t caused by prenatal vitamins, what does cause it? Well, the obvious answer is that during pregnancy you have a tiny person developing inside you.

    But weight gain is also connected to pregnancy-related hormone changes, such as increases in progesterone and estrogen. Since fluids increase during pregnancy, you may also see an increase in your water weight.

    Do prenatal vitamins have other side effects?

    Whenever you introduce a new supplement into your routine, there’s a possibility that you’ll experience some side effects. The most common side effects of prenatal vitamins involve digestive discomforts, which we’ll explore more below.

    Do prenatal vitamins make you sick?

    Morning sickness is a common problem for pregnant people. Some people may even have a hard time swallowing their prenatal supplement as a result of it. A good way to combat this is to take your prenatal vitamins right before bed or with the largest meal of the day.

    Do prenatal vitamins make you poop?

    Because iron is necessary to carry oxygen throughout your body and to your developing baby, iron needs tend to go up during pregnancy. That’s why iron is typically included in prenatal vitamins. However, this can come with some side effects. Iron is associated with digestive problems, including constipation, stomach cramps, upset stomach, gas, bloating, small or hard bowel movements, and dark-colored bowel movements.

    You can combat these symptoms in a number of ways. First of all, you can look for iron in chelated form, which is less likely to cause digestive discomfort. Next, you can eat lots of fruits and veggies for their fiber and antioxidant content, which can help relieve constipation. (The recommended fiber intake of 25-30 g per day.) Staying hydrated is also very important, especially since your water needs go up considerably during pregnancy. Exercise and movement can also be helpful, but you should always discuss your plans with your OB/GYN.

    Key takeaways

    The American College of Obstetricians and Gynecologists recommend that pregnant people take a prenatal vitamin. During pregnancy, your nutrient needs go up, and a prenatal vitamin can help restore proper nutrient levels. If you’re pregnant, prenatal vitamins can also support your health and that of your developing child. Like any supplement, there are some side effects associated with prenatal vitamins, but weight gain isn’t one of them. Care/of’s prenatal vitamin is proven effective, containing 22 essential nutrients that your body needs.

    You're unique. Your supplements should be too.

    Take the quiz
    Dr. Carla Montrond Correia ND, CNS
    Medical Content Manager
    Dr. Montrond-Correia is a licensed naturopathic physician and a certified nutrition specialist (CNS). She holds degrees from University of Bridgeport, Georgetown University, and University of Saint Joseph, and supplemented her education with internships in the health and wellness space. She's focused on research, herbal medicine, nutrigenomics, and integrative and functional medicine. She makes time for exercise, artistic activities, and enjoying delicious food.
    Our Editorial Staff
    Freelance Contributor
    The Care/of Editorial Team is made up of writers, experts, and health enthusiasts, all dedicated to giving you the information you need today. Our team is here to answer your biggest wellness questions, read the studies for you, and introduce you to your new favorite product, staying up to date on the latest research, trends, and science. Each article is written by one of our experts, reviewed both for editorial standards by an editor and medical standards by one of our naturopathic doctors, and updated regularly as new information becomes available.