What prenatal vitamins do to your body

Prenatal vitamins are specialized vitamins designed to meet the increased nutrition needs of pregnant and lactating women. 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.


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

ron 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.

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