Sometimes drugs are essential for the health of the pregnant mother. In those cases, it is imperative for women to discuss their condition with their doctor and weigh the benefits and risks of medication. Drugs taken by a woman who is pregnant most often reach the fetus by crossing the placenta, just as nutrients and oxygen do. When a pregnant woman takes medication, it can cause premature birth by forcefully contracting muscles in the uterus, starve the fetus of nutrients and oxygen thus resulting in an underweight or underdeveloped baby, or cause abnormal development (or birth defects) and even death.

The Food and Drug Administration (FDA) classifies drugs according to the degree of risk they may cause the fetus during pregnancy, as it did with Paxil in 2005 after reports that women taking Paxil during the first trimester of pregnancy had a greater risk of delivery a baby with a birth defect, especially a heart defect. Some drugs are highly toxic and should be avoided during pregnancy. In some cases, doctors may prescribe an alternative medicine that is safer for the unborn baby.

Source: Merck

SOURCE: Paxil and Pregnancy › Pregnant women beware: Some medications can be lethal to fetus