Prenatal Vitamins: Why Pregnant Women Should Take Them

Tuesday, January 30, 2007 - 4:21pm

By Wendy Hodsdon, ND

All women want to provide the best environment possible for their developing baby. Prenatal vitamins, along with a nutritious diet and exercise program, create an optimal environment for the fetus. Prenatal vitamins provide the extra nutrients a mother needs to nourish and birth a healthy baby.

What changes during pregnancy?

A woman’s physiology changes dramatically during pregnancy to support the development of a healthy fetus. The blood volume increases, requiring the production of more blood cells. Hormone levels change. Estrogen reaches levels 10-70 times higher than pre-pregnancy levels, while progesterone is generally 10 times higher than it was pre-pregnancy. The body also starts to make prolactin, which stimulates the production of breast milk. Another hormone, relaxin, is made by the placenta; it works to soften and relax connective tissue and ligaments, causing the uterus to expand.

The increased demand for blood and hormones raises nutritional demands for the mother. Since her fetus is completely dependent on her for nutrition, her body will give it what it needs, depleting her stores, if necessary. This will exacerbate any nutritional deficiencies she may already be experiencing.

Nutrients during pregnancy

The Food and Nutrition Board of the Institute of Medicine recommends certain levels of nutrients for pregnant women. This is usually referred to as the Recommended Daily Allowance (RDA). Many prenatal vitamins have more than 100% of the RDA for some vitamins to allow for the variation in women’s ability to absorb them. Many of these nutrients are deficient or marginally deficient in women before pregnancy. Supplementation makes a difference for both the developing baby and the mother. Some of the most important nutrients are listed below along with their function during pregnancy.


RDA per day

Function During Pregnancy



Folic Acid

400 mcg

800 mcg

Aids in cell formation and DNA synthesis. Low levels cause low weight infants and neural tube defects.

Thiamin (B1)

1.1 mg

1.5 mg

Helps produce healthy nerves and brain cells and helps make energy in cells.

Riboflavin (B2)

1.1 mg

1.6 mg

Helps the production and growth of red blood cells and with metabolism (making energy).

Niacin (B3)

14 mg

17 mg

Helps with a healthy birth weight, length and head circumference.

Pyridoxine (B6)

1.3 mg

2.2 mg

Used for blood and nerve synthesis and helps with protein metabolism. Nausea and morning sickness can be relieved by supplementing with B6.

Vitamin B12

2.0 mcg

2.2 mcg

Helps with nerve and red blood cell function. (Deficiency of B12 can cause anemia.)

Vitamin A – best taken as Mixed Carotenes

700 mcg

800 mcg

Used for healthy skin, eyes and immune system. Best taken as mixed carotenes. Caution: Excess levels of vitamin A have been shown to cause birth defects. Do not exceed 6,000 IU vitamin A per day.

Vitamin C

75 mg

75 mg

Helps with healthy connective tissue, nerves, gums and tooth formation, and is an antioxidant.

Vitamin K

65 mg

65 mg

Helps with bone metabolism and assists with blood clotting.


800-1200 mg

1000 mg

Helps with pregnancy complications (leg cramps, pre-eclampsia, and pre-term delivery).


15 mg

30 mg

Needed to make more red blood cells and to prevent anemia during pregnancy.


280 mg

320 mg

Helps prevent pregnancy complications like leg cramps and tension headaches.

mg = milligrams
mcg = micrograms
IU = international units

Conclusion: take more vitamins for a healthy pregnancy

The amount of nutrients a woman needs during pregnancy is significantly higher than pre-pregnancy. Prenatal vitamins are recommended for all women—even those with an excellent diet—to provide the extra nutrients needed to sustain a healthy pregnancy. By providing extra nutrients to the body, both mother and baby can be healthy and happy during pregnancy.