The categories also provide guidance on weighing the benefits and risks of use in pregnancy. The benefits of its use to fight life-threatening cancers may outweigh the potential harm to a fetus. It is highly effective for treating severe cystic acne, but it causes serious birth defects. There are other drugs available to treat acne, and the disease is not life-threatening to the mother. It's important for pregnant women to realize that most birth defects are not caused by a single factor, nor are they usually caused by faint traces of toxins.
Scientists believe it takes a combination of factors to trigger a congenital malformation.
Most of the chemicals a pregnant woman encounters pose little threat compared with the harm in smoking, drinking alcohol, or eating a poor diet. Public health warnings are aimed at the many to help the relatively few avoid a problem. Daily, heavy exposure to chemicals may be dangerous, however. If a pregnant woman must work around fumes or chemicals, such as in a dry-cleaning business, art studio, or factory, she should use gloves, masks and adequate ventilation. But if she just gets a whiff of dry-cleaning fluid while picking up her laundry from the cleaners, there's little need to worry, Leavitt says.