Prenatal vitamins: What are they and do they make you gain weight?

Jesse Feder, RDApr 20, 2022

As you near childbearing age, there are a vast amount of things that are needed to have a healthy baby. The entire process of conceiving a child, giving birth, and raising your child is life-changing. However, you want to make sure the baby has all the things it needs before entering this world. One of the most important parts of having a healthy pregnancy is taking the right prenatal vitamins.

What are prenatal vitamins?

Prenatal vitamins are a mix of specific essential vitamins that women who are trying to become pregnant or are already pregnant should take daily. They provide their bodies with the necessary vitamins and essential nutrients needed for a healthy pregnancy. However, it is important to note, they are not one size fits all.

What should you look for in prenatal vitamins?

Everyone's bodies are different, some may require more of one vitamin or a certain nutrient than the other. It is always recommended to check with your primary care physician to see what they think is right for you since they are important for both you and the unborn baby. Rootine can then take your doctor's recommendations and customize the right formula that will provide you with all the nutrients you need and fill in any nutritional gap you may have. This can ensure you are getting the right mixture and amounts of prenatal vitamins right from the start. Here is a list of some of the vitamins and minerals you should look for when looking into prenatal vitamins. Again, they are not one size fits all, you might need more or less depending on what your doctor recommends. [1,2]

  • Folic acid
  • Vitamin D
  • Calcium
  • Choline
  • Vitamin C
  • Vitamin A
  • Vitamin B6
  • Vitamin B12
  • Iodine
  • Iron

What do these vitamins do for you?

Folic acid- The folic acid supplement is one of the most important parts of a prenatal vitamin. You want to make sure the prenatal vitamin you are taking has enough folic acid in them. It is recommended to take 400mcg minimum while trying to get pregnant and 600mcg minimum, while pregnant. Folic acid has been shown to reduce the chance of neural tube defects by making sure the brain and spinal cord develop properly. Additionally, folic acid supplementation has been shown to reduce the risk of premature birth as well as prevent some major birth defects including spina bifida and anencephaly. [2,3]

Vitamin D- Your prenatal vitamin should have around 400-600IU of vitamin D. Vitamin D during pregnancy, helps develop the baby's teeth, bones, heart, kidneys, and nervous system. It has also been shown to reduce the risk of preeclampsia. Additionally, it helps make sure you absorb both phosphate and calcium. [4]

Calcium- Calcium during pregnancy helps support bone development and teeth development of the fetus. Additionally, calcium is involved in the proper development of the muscle, heart, and nervous system. The recommendation for calcium is 1000mg a day. Your prenatal vitamin can have varying amounts. It is important that you reach the recommended amount during pregnancy. [3,4]

Choline- Choline has been gaining traction as a beneficial nutrient for having a healthy pregnancy. It is generally recommended to get 450mg of choline a day. Having choline in your prenatal vitamin has been associated with several positive pregnancy outcomes as well as a protectant against certain neural and metabolic defects. Choline is also involved in tissue creation, brain development, and neurotransmission. [5]

Vitamin C- It is recommended to get 85 mg of vitamin C when pregnant. This vitamin can help the baby make collagen. Collagen is what is used to create healthy tendons, bones, and skin. It also helps bolster immunity, hair growth, and aids in iron absorption. [3]

Vitamin A- Vitamin A is a very important vitamin for proper fetal development. the recommended daily amount is 770 micrograms. This vitamin is involved in the development of the baby's eyes, bones, kidneys, lungs, heart, and nervous system. [6]

Vitamin B6- Vitamin B6 can be effective in the relief of morning sickness in pregnant women. Apart from relieving morning sickness, this vitamin aids in the development of the baby's brain and nervous system. It is currently recommended to get 1.9 mg of vitamin B6 a day. [3]

Vitamin B12- The recommended amount of vitamin B12 one should get a day is 2.6 micrograms. Paired with adequate folic acid supplementation, B12 helps with the development of the fetus's nervous system. It also helps prevent the development of neural tube defects. [7]

Iodine- Iodine is important for the development of the fetus's brain, nervous system, and thyroid. The thyroid hormones are essential in the proper development of the baby. When not taking enough, iodine deficiency can lead to cretinism and growth retardation. This is why it's important to get 220 micrograms a day. [8]

Iron- During pregnancy, your body produces more blood to supply more nutrients to the fetus. So, as blood volume increases, our need for iron increases. If there is a lack of iron intake during pregnancy, you are at increased risk of iron deficiency anemia. It is also important not to take too much iron as this can lead to potentially harmful side effects. The recommended amount of iron intake during pregnancy is 27 mg. [9]

Can prenatal supplements cause any harmful side effects?

Like any nutritional supplement, it's best to consult with your primary care physician before starting anything new, and that includes prenatal vitamins. In general, if you follow the directions of your doctor and the supplement label, you may experience mild to no side effects at all. The most common side effects include the following:

  • Bloating
  • Gas
  • Upset stomach
  • Stomach cramps
  • Increased urine production
  • Decreased appetite

Too much of anything can be bad for you, that includes vitamins. Taking too much of a prenatal vitamin can lead to serious health problems. Specifically, vitamins A, D, E, and K, as these are the fat-soluble vitamins that can lead to toxicity. You may start to notice mild symptoms at first such as hair loss, skin rash, skin itchiness, and bruising easily. However, with a continued overdose of these vitamins, they can lead to life-threatening health complications. [10]

Do prenatal vitamins make you gain weight?

All vitamins contain zero calories with the exception of gummy vitamins. So, directly, prenatal vitamins will not cause weight gain. It is important to note, that gaining weight during pregnancy is completely normal. In fact, pregnant women should gain anywhere from 15-40lbs depending on their current weight status and other factors before becoming pregnant. Additionally, you want to consume more calories during pregnancy in order to support the proper development of the fetus. Specifically, during the first trimester, you do not need to increase your caloric intake. However, after that, you will want to add an additional 340, and 450 for the second and third trimesters respectively. You do not want to gain too much weight than you need to, so make sure to follow the directions of your doctor. Prenatal vitamins will not cause weight gain. Significant weight gain is more likely due to the growth of the fetus and increased caloric demand needed during pregnancy. [10,11]

When should you start taking prenatal vitamins?

If this is your first pregnancy and you are unsure when to begin taking prenatal vitamins, it is always best to talk to your primary care doctor. They will generally recommend that you begin taking prenatal vitamins 1-3 months before you begin trying to conceive.

The bottom line

It can be quite overwhelming when trying to make sure you are getting all of the certain nutrients and vitamins needed for a healthy pregnancy. Every woman has different specific needs and some of the generic prenatal vitamins on the market do not have all the things they need. That is why Rootine can be a great tool and service for you to customize exactly what you need to ensure you have a healthy pregnancy.


  1. Dror, D.K. and Allen, L.H. (2012), Interventions with Vitamins B6, B12 and C in Pregnancy. Paediatric and Perinatal Epidemiology, 26: 55-74.
  2. Greenberg JA, Bell SJ, Guan Y, Yu YH. Folic Acid supplementation and pregnancy: more than just neural tube defect prevention. Rev Obstet Gynecol. 2011;4(2):52-59.
  3. Oh C, Keats EC, Bhutta ZA. Vitamin and Mineral Supplementation During Pregnancy on Maternal, Birth, Child Health and Development Outcomes in Low- and Middle-Income Countries: A Systematic Review and Meta-Analysis. Nutrients. 2020;12(2):491. Published 2020 Feb 14. doi:10.3390/nu12020491
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  9. Institute of Medicine (US) Committee on Nutritional Status During Pregnancy and Lactation. Nutrition During Pregnancy: Part I Weight Gain: Part II Nutrient Supplements. Washington (DC): National Academies Press (US); 1990. 14, Iron Nutrition During Pregnancy. Available from:
  10. Shah PS, Ohlsson A; Knowledge Synthesis Group on Determinants of Low Birth Weight and Preterm Births. Effects of prenatal multimicronutrient supplementation on pregnancy outcomes: a meta-analysis. CMAJ. 2009;180(12):E99-E108. doi:10.1503/cmaj.081777
  11. Kominiarek MA, Peaceman AM. Gestational weight gain. Am J Obstet Gynecol. 2017;217(6):642-651. doi:10.1016/j.ajog.2017.05.040