Chicago ? Pregnant women who stop taking antidepressants run a high risk of slipping back into depression, a study found, busting the myth that the surge of hormones during pregnancy keeps mothers-to-be happy and glowing.

The study offers new information but no clear answers for expectant mothers who must balance the risk of medications harming the fetus against the danger of untreated depression.

“It’s important that patients not assume that the hormones of pregnancy are going to protect them from the types of problems they’ve had with mood previously,” said study co-author Dr. Lee Cohen of Massachusetts General Hospital.

Researchers followed 201 pregnant women with histories of major depression.

Because of ethical concerns, the researchers did not randomly assign the women to either stop or continue medication. Instead, the women decided what to do, then researchers watched what happened.

Sixty-eight percent of those who stopped taking antidepressants slipped into depression. They were five times more likely to suffer a relapse than those who continued on drugs.

But staying on antidepressants did not shield expectant mothers from depression entirely; 26 percent of those who continued drug treatment became depressed anyway.

The study appears in today’s Journal of the American Medical Assn.