Gene defect perils mother and baby.

For years, physicians have been puzzled by seemingly healthy women who, in their third trimester of pregnancy suddenly are struck by swelling, severe nausea, vomiting, or jaundice. Their illness rapidly can progress to liver failure and, in some cases, coma or death. The only "cure" for mothers is immediate delivery of their babies. Following childbirth, most mothers fully recover.

The cause of this rare illness, maternal acute fatty liver of pregnancy, is a genetic mutation inherited by the babies, researchers at Washington University School of Medicine have found. "Somehow, the fetus is poisoning the mother. As soon as the fetus is delivered, essentially, the women start to get better," notes Arnold Strauss, professor of pediatrics, molecular biology, and pharmacology.

Identification of the mutation, which affects one in 13,000 females and their babies, will enable physicians to screen pregnant women who suddenly develop symptoms of the illness. Their babies also can be monitored closely and treated for problems following delivery.

The mutations produce a faulty enzyme in the babies that prevents the conversion of certain fats into energy. Those born with the mutations suffer from a variety of conditions ranging from sudden death to liver failure to heart muscle and skeletal muscle disorders. All result from a faulty...