Roy Pitkin, M.D., is a professor of obstetrics and gynecology and is the former chair of the ob/gyn department at the University of California, Los Angeles School of Medicine. He is a frequent advisor to national health agencies on women's health issues and has received numerous international honors for this work.

Q: I'm 20 weeks pregnant and have been suffering from constipation. Could the iron in my prenatal vitamins be contributing to this condition?

A: Constipation is a side effect of oral iron therapy, so it is possible that your prenatal supplements could be responsible. Iron is especially important during pregnancy because a woman's body is expected to make additional blood and to also supply iron to her fetus. Iron makes hemoglobin, the material in blood that carries oxygen throughout the body.

To help alleviate the constipation, you might try making some simple dietary adjustments, like adding more fiber to your diet and drinking more water. If these fail to help, talk to your doctor about taking a stool softener or bulk-forming laxative. As a last resort, you might check with your ob/gyn to see if your hemoglobin levels are high enough to stop taking iron-containing supplements.