Do Prenatal Vitamins Make Women Gain Weight?

It's common to wonder if the many things that typically happen during pregnancy -- weight gain, improved complexion, and hair growth -- are due to pregnancy itself or to the prenatal vitamins that women take. In general, pregnancy vitamins are quite similar to daily multivitamins, and don't tend to cause significant positive or negative side effects.

Components of Prenatals

Prenatal vitamins, whether prescription or over-the-counter, share much in common with the regular daily multivitamins that many non-pregnant women take. The differences are important in the event that you're pregnant, however -- prenatals provide more of the crucial vitamins and minerals that help ensure a healthy mother and baby. Specifically, iron and folic acid levels are much higher in prenatal vitamins than they are in daily multivitamins, explain Drs. Michael Roizen and Mehmet Oz in their book "You: Having A Baby."

Role of Vitamins In Nutrition

Pregnant woman with prenatal vitamins

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No vitamin -- neither a regular multivitamin nor a prenatal -- can make you gain weight. This is because vitamins do not contain any calories, and you can't break them down for energy or store them as fat. Instead, vitamins and also minerals -- which are also common components of prenatal and regular vitamins -- serve other important roles in the body. Some help chemical reactions to take place, while others prevent damage to cells from toxins.

Weight Gain

Though most people understand that regular vitamins don't cause weight gain, it's common to wonder whether prenatal vitamins can, since women who are taking them so commonly gain weight. In reality, the weight gain isn't due to the vitamins -- it's due to pregnancy itself. Dr. Miriam Stoppard, in her book "Conception, Pregnancy and Birth," explains that during the course of a typical pregnancy, a woman gains 25 to 35 pounds. This is true regardless of whether she's taking vitamins.

Iron and Folic Acid

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Because the major differences between prenatals and regular multivitamins are the quantities of iron and folic acid, understanding the role of these nutrients can help you to understand why prenatals can't cause weight gain. Your baby uses folic acid to help produce the neural tube, which becomes the brain and spinal cord. You use iron to produce extra red blood cells, which deliver oxygen and nutrients to your cells and your baby's, explain Drs. Roizen and Oz. Neither of these nutrients provide energy.

Expert Insight

If you're taking prenatal vitamins and are experiencing significant weight gain, while the vitamins aren't to blame, it's worth talking to your doctor. Some prenatal vitamins can cause constipation, which may make you feel bloated and make your clothing fit a bit tighter. Changing prenatal vitamin brands can sometimes help alleviate symptoms. Don't stop taking your prenatal vitamin without checking with your doctor first, even if you're worried it's causing weight gain -- you and your baby both depend upon the nutrients it provides.