Last Updated on November 11, 2021 by Kinacle.

Do Prenatal Vitamins Cause Weight Gain

Pregnancy is such an exciting moment for yourself and those close to you. In fact, it seems like everyone else wants to join in the fun too! More than likely you’ll run into people hoping to give you their tips, advice and opinions whether you ask for them or not!

One thing you may have been told is that prenatal vitamins can cause weight gain – but is there actually any truth behind this? Here’s the answer:

There is recent evidence that multivitamin supplements can increase pregnancy weight gain. Women who take prenatal vitamins may have higher gestational weight gain than women who don’t take multivitamins.

However, the reality is more complicated than this statement may appear.

So before you get on the scale and freak out, here are the facts. Regardless of taking prenatal vitamins, pregnant women normally gain weight due to the growing baby inside their womb, along with the rest of the normal bodily changes that they encounter while pregnant.

However, are you worried that taking prenatals will cause you to gain more weight than you would otherwise?

If so, let’s unveil some more important facts about prenatal vitamins, how they seem to influence weight gain, and what you can do to stick with your normal weight while taking prenatal vitamins.

What are prenatal vitamins?

Prenatal vitamins (often shorted to just ‘prenatals’) contain the essential micronutrients that a future mom needs to support a healthy pregnancy. Prenatal vitamins are not simply like the other multivitamins as they are tailored to fit the specific needs of pregnancy.

It is important to take note that prenatal vitamins aren’t made to help women gain weight while pregnant or trying to be pregnant. The vitamins and minerals found in prenatal pills have their own specific purpose for the development of the fetus and safeguarding the health of pregnant women.

According to the American Pregnancy Association, a quality prenatal vitamin must meet the recommended micronutrients based on the guidelines set by the Food and Nutrition Board (FNB) of the Institute of Medicine, namely:

Vitamin A

Vitamin A is known for its role in visual development. Its derivative, called retinols, help with the development of the eyes, ears, limbs and heart.

Vitamin B Complex

This group of vitamins helps convert food to energy so that your body can utilize the nutrients more efficiently to support pregnancy. The B vitamins are also essential for your baby’s blood and brain development, especially the Vitamin B9 (also known as folate) which you can get from natural food sources. Since most pregnant women are unable to get sufficient amount of folate from their diet, its synthetic form (also known as folic acid) is often given as a supplement.

Folic acid may help prevent neural tube defects or the severe malformations involving the brain and spine of the fetus. Neural tube defects affect approximately 300,000 babies each year around the world, making folic acid an essential vitamin for all women of childbearing age.

Vitamins C and E

These vitamins are potent antioxidants that play a major role in immunity and collagen production. Collagen is one of the building blocks of skin, bones, cartilage and tendons. Vitamin C is also found to increase the absorption of iron, which is vital during pregnancy.

Vitamin D

Vitamin D helps regulate the calcium and phosphate levels for bone metabolism and teeth development. A deficiency in vitamin D during pregnancy may increase your risk of pregnancy-related complications such as pre-eclampsia, gestational diabetes, and premature birth.


This mineral is important for baby’s bone development while inside the womb. The supplementation of calcium during pregnancy may potentially reduce the occurrence of hypertensive disorders in pregnancy such as pre-eclampsia and eclampsia.


Iron is a prime component in the production of hemoglobin, the part of the blood that carries oxygen to the rest of the body. The increased demand for blood and oxygen during pregnancy also increases the need for iron. Most prenatal supplements can supply the needed iron for pregnancy.


In modest amounts, iodine is necessary for the production of thyroid hormone both for the mom and her unborn child. These thyroid hormones are needed to regulate the nervous system of the fetus that is developing inside the womb.

Magnesium, Sodium, Potassium

Sodium and potassium are electrolytes that help regulate the hydration status of the body which, in turn, is important for muscle contraction and nerve impulses. Magnesium assists in the sufficient blood flow to the brain which is needed during pregnancy.


Zinc is essential for normal immune system functioning and many important body functions such as production of protein and cellular division. Some studies suggest that zinc supplementation while pregnant may help prevent premature birth.


Choline can be synthesized by the body in small amounts and can also be derived from natural food sources. However while pregnant, vast amounts of choline is needed to support the development of the baby’s brain and liver, as well as the placenta.

Sometimes, prenatal vitamins may vary in terms of the ingredients that they contain. For instance, some varieties may contain more iron because they specifically cater to women who are more at risk of iron-deficiency anemia. It is also common to encounter prenatal vitamins containing only some of these essential vitamins and minerals.

Are prenatal vitamins good for you?

Prenatal vitamins can have beneficial effects to your health if you are pregnant, trying to get pregnant, currently breastfeeding or you are in your child-bearing age.

Prenatal vitamins are good for pregnant women.

Pregnant women will need higher amounts of certain nutrients like folic acid, calcium, and iron to sustain the growth and development of their baby. Other vitamins and minerals that you will need for pregnancy include vitamin D, choline, omega-3 fatty acids, B vitamins, and vitamin C.

As such, your Ob-Gyn will recommend prenatal vitamins on top of a healthy diet to make sure that the increased needs for these nutrients are met. Taking prenatal vitamins can help prevent some of the major pregnancy-related complications that can lead to fatal outcomes.

Prenatal vitamins can be beneficial for breastfeeding mothers.

Doctors may also recommend taking prenatal vitamins after giving birth if you are breastfeeding. This is to help replenish the vitamins and minerals needed to support breastfeeding.

Folic acid may be good for all women of child-bearing age.

Women of child-bearing age may be advised to take additional folic acid or eat more folate-rich foods due to the prevalence of unplanned pregnancies.

In the U.S., around 45 percent of pregnancies are unintended. Teenagers aged 15 to 19 have higher incidence of unintended pregnancies at approximately 75 percent.

Hence, taking more folate or folic acid ahead of time are deemed essential for all women who can get pregnant. This B vitamin can significantly help in the development of the baby’s brain and nervous system which happens during the first few weeks of pregnancy, often long before women discover that they are pregnant.

However, taking prenatal vitamins if you are not pregnant or not actively trying to conceive might do more harm than good.

Prenatal vitamins have higher amounts of vitamins and minerals that are intended to support the growth and development of another human being.

Having too much of these vitamins and minerals without a specific purpose may lead to some side effects. For example, too much iron can lead to constipation, while excessive amounts of the fat-soluble Vitamin A can lead to liver toxicity.

Do prenatal vitamins make you gain weight while pregnant?

As you might already know, weight gain is a normal part of pregnancy. On average, women are expected to gain around 25 to 35 kilograms over the duration of pregnancy. The recommended pregnancy weight gain may also be lower or higher depending on your body mass index (BMI) before getting pregnant.

It is important to take note that these extra pounds will be coming from your growing baby, the amniotic fluid, the placenta and the excess body fluids and fat stores that you need support pregnancy and breastfeeding.

But the question that might be bothering you now is, do prenatals make you gain weight more than what you should while pregnant?  Let’s begin with what researchers have found.

A study among HIV-negative pregnant women in Tanzania showed a positive relationship between multivitamin supplementation and pregnancy weight gain. The respondents who are taking multivitamins had a significant increase in pregnancy weight gain during their third trimester when compared to the respondents who are not given multivitamins. This result was similar to other previous studies among HIV-positive pregnant women in Tanzania and among underweight pregnant women in Chile.

Based on these evidences, it can be presumed that prenatal vitamins can improve the weight gain among pregnant women to a certain extent. The researchers associated the increase in weight gain to the nature of the vitamins that are enclosed within the supplement and how they might have assisted the absorption of other nutrients during pregnancy.

For example, the B vitamins are known to assist in protein and energy metabolism, which may have further helped the fetus absorb other nutrients more efficiently. As antioxidants, Vitamins C and E may have reduced oxidative stress, improved the pregnant woman’s immune system, and thus, may led to an improved growth of the baby inside the womb.

All these circumstances are believed to help the future mom increase the weight she gains during pregnancy. However, do take note that the “weight gain” that was being discussed here may still be within the normal gestational weight gain that are expected of pregnant women.

Therefore, these findings may imply that prenatal vitamins can be extra beneficial for pregnant women who are underweight or losing weight while pregnant as well as for the populations wherein low birth weight infants are prevalent.

Do prenatal vitamins make you fat?

The amount of energy that a food or drink contains is measured in calories. If you take in more calories than what you burn or use, it can make you gain weight and store it as fat.

For females, the average caloric requirement is 2000 calories per day. However, pregnant women need to increase their caloric intake meet the demands of pregnancy. The current recommendation for a single pregnancy is no additional calories for the 1st trimester, additional 340 calories per day for the 2nd trimester and 450 calories per day during the third trimester.

Here are some important points to ponder when it comes to prenatals and weight gain:

Prenatal vitamins do not contain any calories that can make you gain more weight or fat.

Just like any other multivitamins, prenatal vitamins has zero calories. The extra calories needed by pregnant women must be gained from a healthy diet and not from the vitamins that she takes.

Prenatal vitamins may have side effects that can make you feel “fat”.

The vitamins and minerals included in prenatal vitamins may have some side effects. The iron found in most prenatal pills can make you constipated and bloated, such that your clothes may feel tighter than usual.

Prenatal vitamins may affect your appetite.

Multivitamins help restore the normal metabolism of the body, enhance the feeling of wellbeing and may improve appetite.

However, the metallic taste of iron in prenatal vitamins may also trigger nausea during pregnancy which may result to a decrease in appetite.

Therefore, taking prenatal vitamins does not directly add additional calories into your diet, but some of its side effects may make you feel fatter or eating more than you should. This “feeling” doesn’t directly mean that you are gaining weight or fat while taking prenatal vitamins.

Do prenatal vitamins make you gain weight when not pregnant?

There is no evidence that prenatal vitamins can cause weight gain when taken by non-pregnant women.

While trying to get pregnant, prenatal pills may be recommended to make sure that your vitamin and mineral levels are sufficient to support a possible pregnancy. During the early weeks, pregnancy may not be detected immediately, but most of the vital aspects of fetal development are already happening inside the womb.

If you feel that you might be gaining weight or your clothes have been feeling tighter while taking the prenatal vitamins, then taking a pregnancy test at home or at your doctor’s clinic may help. While you may simply be constipated or bloated, it is also possible that you are experiencing early signs of pregnancy.

Tips in maintaining healthy weight while taking prenatal vitamins

Pregnant or not, it is important to maintain a healthy weight to prevent complications and illnesses that can compromise your wellbeing. So if you feel like you’re gaining too much weight while taking prenatal vitamins, then here are some tips that can help you keep those extra pounds at bay:

Track down your calories.

Tracking the calories from the food you eat is one of the best ways to stick with a normal weight. You may take advantage of calorie calculator apps that you may find online to make it a lot easier for you to keep an eye at your daily caloric intake.

Avoid “eating for two”.

You might already heard of the common pregnancy myth that you should be eating for two while pregnant. More often than not, this belief will just make you eat a lot more than what you actually need. In fact, eating twice as much food as you usually take during pregnancy can be dangerous to your health.

Take note that even if the caloric requirement increases during pregnancy, it is simply within 340 to 450 calories a day. These extra calories are roughly equivalent to one full glass of skim milk and half of a sandwich.

Eat twice as healthy instead.

Take the additional calories you need from healthy sources such as fruits, vegetables and whole grains. Not only will it help you stick within the recommended weight gain while pregnant, it will surely help minimize the chances of getting health problems in the future.

Take time to exercise.

Exercise helps burn extra calories that your body doesn’t need and yes, even pregnant women are recommended to exercise.

However, take note that pregnant women experiencing medical conditions and those who have a higher risk for bleeding may not be allowed to exercise. To be safe, verify with your doctor before beginning any exercise program while pregnant.


To round it up, some scientific evidences showed that pregnant women may have improved pregnancy weight gain when taking prenatal vitamins, which is necessary for a healthy pregnancy. So even if prenatal vitamins do not directly cause weight gain, the vitamins and minerals that they contain may, in one way or another, affect one’s metabolism, appetite and overall sense of wellbeing.

If you’re worried that you are gaining too much weight while taking prenatal vitamins, then you should seek advice from your doctor. Other than the prenatal vitamins, the sudden increase in your weight may be associated with other factors such as your diet, activities and health condition, so it is best to verify the cause before putting the blame of your weight gain on the vitamins that you are taking.

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