Yet they rarely wean themselves from popular selective serotonin reuptake inhibitor (SSRI) antidepressants like Prozac, Celexa and Zoloft despite an increasing number of studies linking prenatal exposure to birth defects, complications after birth and even developmental delays and autism.

Up to 14 percent of pregnant women take antidepressants, and the Food and Drug Administration has issued strong warnings that one of them, paroxetine (Paxil), may cause birth defects.

But the prevailing attitude among doctors has been that depression during pregnancy is more dangerous to mother and child than any drug could be. Now a growing number of critics are challenging that assumption.

“If antidepressants made such a big difference, and women on them were eating better, sleeping better and taking better care of themselves, then one would expect to see better birth outcomes among the women who took medication than among similar women who did not,” said Barbara Mintzes, an associate professor at the University of British Columbia School of Population and Public Health. “What’s striking is that there’s no research evidence showing that.”

On the contrary, she said, “When you look for it, all you find are harms.”

SSRIs are believed to work in part by blocking reabsorption (or reuptake) of serotonin, altering levels of this important neurotransmitter in the brain and elsewhere in the body. Taken by a pregnant woman, the drugs cross the placental barrier, affecting the fetus.

“Serotonin is a critical neurotransmitter and cell-signaling molecule,” said Dr Adam Urato, a maternal-fetal medicine specialist at Tufts Medical Center. “From the brain, it signals the neurons where to go, what to do and how to develop. It signals the heart; it plays an active role in the gut; and it plays an important role in the formation of the lungs. What it does during development is basically everything.”

Three new studies have heightened concerns about long-term developmental effects. Researchers at Johns Hopkins University reported in April that boys with autism were nearly three times more likely to have been exposed to SSRIs before birth than typically developing boys.

Harvard researchers linked prenatal exposure to nearly twice the risk for attention deficit hyperactivity disorder among children. The researchers also found that exposed children were more likely to have autism spectrum disorders, but after adjusting the data to account for the mothers’ psychopathology, the scientists then concluded the increase was not statistically significant.

“If the mother has a psychiatric illness, she is more likely to have a child with autism” or other illness, independent of her use of SSRIs, said Dr Roy Perlis, an associate professor of psychiatry at Harvard Medical School.

A large Norwegian study, reported in April, that looked at a registry of more than 51,000 babies found that prolonged use of SSRIs during pregnancy was associated with lower language competence by age 3, an effect the researchers said was independent of the mothers’ depression.

Doctors have long worried that depressed women may be at higher risk of giving birth prematurely, which puts babies at risk of both short- and long-term health problems.

But three separate large meta-analyses published over the past year and a half, one by Dr Urato, reviewed the data from earlier studies, and all concluded that women on antidepressants were more likely to give birth prematurely than depressed women who weren’t on medication.

Preterm births are not the only risks linked to these antidepressants. Babies exposed to SSRIs prenatally are more likely to be born with congenital heart defects, other rare birth defects, clubfoot and a serious lung condition called persistent pulmonary hypertension, several studies have found.

Like babies born to drug addicts, newborns may display SSRI withdrawal symptoms. One study found that SSRIs disrupt fetal non-REM sleep, the deep sleep that is important for healthy growth.

Another study concluded that the babies of treated mothers also had lower Apgar scores, a measure of a newborn’s well-being. Yet another found these infants were more likely to be underweight.

Some psychiatrists worry that the spate of new findings will deter some women from seeking help they need.

“The downside of these studies is that it ends up scaring women away from treatment,” said Dr Perlis, the author of a recent paper that found increased rates of hyperactivity, but not autism, in exposed children.

Still, he emphasised that for a subset of people, “the severity of the depression or anxiety can make it very hard for them to take care of a child, and is such that their life is at risk if they’re not treated.”

Other experts think it’s time to reconsider widespread use of these drugs in pregnant women altogether.

“This is a message people don’t necessarily want to hear,” Dr. Urato said. “Everyone’s happier with this idea that the medications are OK.”

Yet quitting SSRIs cold turkey is not advised. Women who are pregnant or planning a pregnancy and want to taper off medication should so with a doctor’s supervision, Dr Urato and other experts said, and consider nondrug treatment options, including counseling, regular and frequent exercise, meditation, acupuncture and bright light therapy.