Toxins and Pregnancy

When you're expecting a baby, how vigilant do you need to be about possible toxins? Sure, you'll want to steer clear of smokers, the cat's litter box, and margaritas. But what about the sushi bar, nail polish, and bottled water?

With new alarms sounded almost daily, it's a challenge to know what to do.

WebMD turned to the experts for advice. Unfortunately, the territory is not clearly charted. Besides the known risks, there lurks a vast gray area in which the research is inconclusive. According to the March of Dimes web site, the cause of about 70% of birth defects is unknown. And most known defects are due to genetic or other unpreventable causes -- not to mom's exposure to toxic chemicals, foods, drugs, or infections.

So is there any way to lower the risk? The following information should help you separate the facts from the likely fiction.

Known Risks

Substances that can cause birth defects are called "teratogens." Exposure to them does not automatically put your fetus at risk. The level and length of time of exposure, as well as the stage of the pregnancy at time of exposure, can come into play. According to the educational bulletin on teratology published by the American College of Obstetrics and Gynecology (ACOG), the following are among the known causes of birth defects:

Drugs and Chemicals

• Alcohol
• Androgens and testosterone derivatives, such as danazol
• Angiotensin-converting enzyme (ACE) inhibitors, such as enalapril and captopril
• Coumarin derivatives, such as warfarin
• Carbamazepine
• Folic acid antagonists, methotrexate, aminopterin
• Cocaine
• Diethylstilbestrol (DES)
• Lead
• Lithium
• Organic mercury
• Phenytoin
• Streptomycin and kanamycin
• Tetracycline
• Trimethadione (no longer available in the U.S.) and paramethadione
• Valproic acid
• Vitamin A and its derivatives, such as isotretinoin, etretinate, retinoids

Infections

• Cytomegalovirus
• Rubella
• Syphilis
• Toxoplasmosis
• Varicella

Radiation

Worse Than Thalidomide

The thalidomide scare of the 1960s is legendary. Yet in terms of risk and impact, it pales in comparison to isotretinoin, best-known by the brand name Accutane, according to Lynn Martinez, Utah State Health Department coordinator of the Pregnancy Riskline in Salt Lake City.

"It's an amazing drug approved for severe nodular or cystic acne, but it's estimated that in the U.S., 90% of prescriptions are off label. Someone gets an outbreak of pimples and wants Accutane," she says.

Martinez tells WebMD that if a woman takes the drug during pregnancy, there is a 30% to 35% risk for major birth defects, including complete absence of the thymus gland; serious, often lethal, heart defects; absence of the inner and outer ears; and severe, possibly lethal, hydrocephalus - a buildup of excess fluid in the brain. Furthermore, of the 65% of babies born without structural malformations, 50% are profoundly mentally retarded.

"It's interesting to me that by comparison, Accutane's risk is much higher than thalidomide's -- which carries a 20% risk -- and its harm to the child is far worse," she says.