What happens to your body when you take prenatal vitamins

A healthy diet is one of the keys to having a healthy pregnancy. Unfortunately, many pregnancy-related symptoms, such as nausea, vomiting, and food aversions, can prevent women from eating well-balanced meals. In my practice as a registered dietitian, I see even the most motivated mama has a hard time sticking with an optimal diet. Most doctors and dietitians recommend that women take a prenatal vitamin both during and after pregnancy to help ensure the nutrient needs of both mom and baby are met.

Prenatal vitamins are specialized vitamins designed to meet the increased nutrition needs of pregnant and lactating women. They should only be taken by women trying to get pregnant, who are pregnant, or who are breastfeeding and they should be started about three months before trying to conceive to help correct any potential vitamin or mineral deficiencies that may exist. After pregnancy, prenatal vitamins can help provide extra nutrients for breastfeeding, helping keep mama and baby healthy. 

While prenatal vitamins are a matter of course for many women, you may not realize what's really going on in your body when you take them. Here's what you need to know.

Folate helps prevent birth defects

One of the most important nutrients in prenatal vitamins is called folate, also known as folic acid or vitamin B9. Folate helps the body make DNA, enhances brain function, and plays a role in cell growth. For pregnant women, it can help reduce the risk of birth defects related to the brain and spinal cord. 

Early in the development of the fetus, there is an opening at the bottom of the spinal cord that requires folate to close properly. How folate helps with the closure is unclear, but may be related to the role it plays in cell growth. For this reason, taking a folate supplement during pregnancy has been shown to reduce the risk of these types of birth defects by over 70 percent. This particular birth defect occurs early in pregnancy before a woman even knows she is pregnant, therefore doctors and dietitians recommend starting a prenatal vitamin before trying to conceive. 

This vitamin is commonly found in green leafy vegetables and fortified breads and cereals, but many women are deficient in folate prior to getting pregnant. As I've seen in my practice as a dietitian, most of us don't eat nearly enough green leafy vegetables. Birth control pills and being overweight can also increase risk for folate deficiency, making it even more important to improve levels before trying to conceive.

Iron levels get a boost

Iron is a mineral that is needed to build red blood cells that help carry oxygen throughout the body. A lack of iron is called anemia and is a common blood condition for women of childbearing age. Anemia is more common during pregnancy because iron needs increase from 18 mg per day to 27 mg per day. Women need additional iron to help build red blood cells for both themselves and the baby, to support a healthy placenta, and to prepare for blood loss during birth. 

Generally, mild anemia during pregnancy just causes slight fatigue (but who isn't tired while pregnant?) and doesn't cause any major problems. But if anemia is left untreated or becomes severe, it can increase the risk of a preterm labor or a stillbirth.

Most doctors will automatically check iron levels in pregnant women in order to monitor for anemia. If you do have anemia, it can be treated via diet modification and by taking a prenatal vitamin with iron. Most prenatal vitamins contain some iron, but not all do, so be sure to check the label.

Calcium builds strong bones for mom and baby

Prenatal vitamins also contain calcium, an important mineral for building bones. Calcium is also used for maintaining healthy nerves, hormones, and helping muscles contract. Surprisingly, calcium needs do not increase during pregnancy; they stay at 1000 mg/day for both pregnant and non-pregnant women because the body absorbs more calcium from food during pregnancy. 

That said, if the body is lacking the calcium it needs for the baby, it will steal it from the mother's bones, leaving her bones weaker. For this reason it is important for pregnant women to get enough calcium to help maintain their bone mass.

Unfortunately, most prenatal vitamins only contain a small amount of calcium and do not meet 100 percent of pregnant women's needs for all of the changes in her body. Therefore, it is recommended that pregnant women eat three servings of high calcium foods daily, such as dairy products or fish with bones. If a woman does not tolerate dairy, an additional calcium supplement may be recommended.

DHA boosts baby's brain power

Many prenatal vitamins contain an omega-3 fatty acid called docosahexaenoic acid or DHA. This healthy fat is critical for the development of the brain and nervous system. The brain is 60 percent fat, therefore fat is necessary to help grow a baby's brain. 

The primary source of DHA is fatty fish, but many women are told to limit fish intake due to concerns over mercury contamination. Low intake of omega-3 fats has been linked to a lower IQ, prematurity, autism, and ADHD. Limiting fish can therefore reduce the intake of healthy fats during pregnancy, making DHA's role in prenatal vitamins particularly important to help supplement the mother's diet and support the baby's growing brain.

May reduce the risk of pregnancy complications

Prenatal vitamins not only help reduce the risk of certain birth defects, they can also help reduce the risk of many pregnancy-related complications, such as preterm delivery and having a low birth weight baby.

A study comparing women who took prenatal vitamins and those who didn't found a two times decreased risk of early delivery before 33 weeks. The reduction in risk was four times greater if the prenatal vitamins were started in the first trimester. Risk of low birth weight was also reduced, by seven times, particularly if the vitamins were started early. Reducing the risk of preterm labor and having a low birth weight infant significantly increases the likelihood of a healthy baby and mom after birth. 

Taking prenatal vitamins may help reduce the risk of pregnancy complications because they help correct any nutritional deficiencies in both the baby and the mother. Also, women who have normal levels of both folate and iron tend to have healthier placentas, which in turn may help the baby grow and reduce the risk of preterm labor.  

Helps protect mother's health

Once a woman is pregnant, her body tends to prioritize nutrients towards the growth of the baby. This means that even if a mother has a less than ideal diet, she may still be able to give birth to a healthy baby. But this also means that the mother's nutrient status may suffer if there are not enough vitamins and minerals to support both. 

The nutrients we have discussed, folate, calcium, iron, and omega-3s, may all become depleted in the mother if she is not eating enough for herself and the baby. Not only can this depletion lead to bone loss or anemia as we have explored, it may also put the mother at greater risk for postpartum depression. So really, the prenatal vitamin is just as much for the mother's health as the baby's.

Boosts nutrition during breastfeeding

Even after the baby is born, the diet of a breastfeeding mother remains incredibly important. Nutrient needs actually increase during breastfeeding, when compared to pregnancy. Breastfeeding moms need more iron, calcium, and vitamin C than pregnant women. They also need to drink more water and eat more calories to help produce enough milk for a growing baby. 

A new mother may not have an ideal diet between caring for baby and themselves, so prenatal vitamins can help fill in some of the nutrient gaps that may exist, particularly for important vitamins such as iron, vitamin D, and some  B-vitamins. Prenatal vitamins therefore remain critically important during breastfeeding to prevent deficiencies and provide enough nutrition in the breast milk to support the mother and the baby. 

May cause digestive discomfort

The nausea and morning sickness many women experience during pregnancy can sometimes be made worse due to high doses of iron and some B vitamins in certain formulations of prenatal vitamins. Personally, during my pregnancy it took a few tries to find a prenatal that didn't make me throw up as soon as I took it, and it was not because of morning sickness. In addition to nausea, iron can also be constipating. Talk about a double whammy!

For the best rate of success, prenatal vitamins should always be taken with food. You may have to try a few different brands until you find one that works with your body. Some brands spread the vitamins out into two or three pills a day, which may be easier on the stomach. If you are having difficulty with constipation, you may have to look for a vitamin with less iron. If you are looking for a good prenatal vitamin, start by asking your doctor or friends what they would recommend.

They do not help hair and nails grow

There is an ongoing myth that taking prenatal vitamins when you are not pregnant will help your hair and nails grow. This myth is perpetuated by the fact that during pregnancy many women experience faster growth of their hair and nails, but this is related to pregnancy hormones, not the vitamins.

Prenatal vitamins do not contain any secret combination of vitamins and minerals that boost hair and nail growth. If you want stronger hair and nails, there are specialty vitamin formulations on the market that are designed specifically for this purpose.

If you don't need them, they can be toxic

Prenatal vitamins have higher doses of vitamins and minerals than what is needed for the average woman. The higher doses of these nutrients, when taken over a period of time, can lead to toxicity

For example, if you don't need a high dose of zinc, found in many prenatal vitamins, it can interfere with the absorption of iron and other minerals leading to deficiencies. The same goes for iron. If you don't need such a high amount, over time it can lead to iron poisoning. If you are not pregnant or intending to get pregnant and want to take a vitamin supplement, look for a standard women's multivitamin to help meet your nutrient needs.