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Why do I need to take iron supplements during pregnancy?


Iron & pregnancy

Particularly if you're anemic, your caregiver may give you a prescription for iron tablets. Nutritionist and registered dietician Martha Belury, PhD, RD, tells you why iron is important for your body, and also disusses how these supplements might otherwise affect you.

The question:

I was recently told by my doctor that I need to take iron supplements. Why is this necessary?

The expert answers:


The Recommended Daily Allowance (RDA) for iron for a pregnant woman is 30 milligrams per day. This extra iron is needed for the normal functions of building red blood cells and carrying oxygen to tissues. Because the blood volume of a pregnant woman increases by as much as 50%, extra iron is needed for this extra blood. As importantly, this blood is supplying the growing fetus with oxygen and other gasses as well as nutrients.

The RDA for iron is double the recommendation for non-pregnant women in childbearing years (15 milligrams per day for non-pregnant women). Therefore, while you may increase your consumption of iron-rich foods such as meat, eggs, vegetables, and iron-fortified cereals, it is nearly impossible to achieve the RDA for iron each day without supplementation.

Unfortunately, the levels of iron in supplements can cause problems in the gastrointestinal tract, such as an odd and lingering after-taste, stomach lining irritability, gas, and constipation. Constipation may already be a problem in pregnancy due to hormones such as progesterone, which slow down the digestive process. Adding a supplemental source of iron may make constipation worse. Be sure to get enough fiber from bran, fruits, and raw vegetables, as this may alleviate constipation.

In addition, consuming lots of fluids, especially plain water, and engaging in physical activity are all recommended to help stimulate intestinal activity. Finally, some supplements contain a stool softener, which may also alleviate constipation.

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