The Public Citizen Health Research Group asked the Department of Health and Human Services yesterday to end sales of Bendectin, the only government-approved drug for the "morning sickness" of early pregnancy.

The Washington-based HRG cited new animal studies and reviews of human data indicating a possible link between use of the medicine in the first trimester of pregnancy and infant diaphragm hernia--a hole that lets the intestines protrude into the chest and squeeze the lungs, often fatally. The estimated incidence of the hernia in Bendectin-exposed babies is up to 40 per 10,000.

Health and Human Services Secretary Richard S. Schweiker by law is empowered to revoke marketing approval of a drug if new "tests or other scientific data cast doubt on its safety," HRG director Sidney M. Wolfe wrote in a petition to stop Bendectin sales.

Last year, Wolfe unsuccessfully urged HHS to halt sales of Bendectin on the grounds that the vitamin in Bendectin decreases the anti-nauseant effectiveness of its principal ingredient, an anti-histamine called doxylamine succinate.

Schweiker had no comment on Wolfe's petition, but it was learned yesterday that his staff has asked the Food and Drug Administration for a Bendectin status report. Last Tuesday, the FDA discussed the new evidence with the manufacturer, Merrell Dow Pharmaceuticals, Inc. and a new warning is expected to be added to the prescribing instructions, possibly in July.

Wolfe also urged Schweiker to require the labels of all antihistamine and anti-nausea preparations to warn of an increased risk of birth defects and to advise against use in pregnancy. Wolfe pointed out that the label on Unisom, an over-the-counter sleep aid that also contains doxylamine, warns against use in pregnancy.

In 1979, then-Sen. Schweiker, learned about a 1963 study by the drug's manufacturer that showed some fetal deformities and deaths in rabbits. FDA files indicate the company waited 16 years to submit the data to the agency. Schweiker asked the FDA to "investigate the quality of safety testing" of Bendectin, and was told it was adequate.