Intake of antidepressants like Prozac by expectant mothers, late in their pregnancy is likely to cause a rare but serious breathing problem in the infants, according to the findings, published in The New England Journal of Medicine.
The lung disorder, called persistent pulmonary hypertension, which can be fatal, strikes 1 to 2 newborns in 1,000, on an average. In babies exposed to antidepressants during the last few months of pregnancy, the study found, the rate was six times as high: 6 to 12 newborns in 1,000.
Studies have also found that up to one-third of babies exposed to antidepressants in the womb suffer temporary withdrawal symptoms like agitation.
Untreated maternal depression can also harm a developing foetus, experts say. Researchers recently reported in a study that 68 per cent of pregnant women, who quit taking antidepressants relapsed, compared with 26 per cent of those who stayed on the drugs.
According to Dr. Sandra L. Kweder, an official at the Food and Drug Administration, that the agency planned to search its own database of adverse events for further evidence of risk. She said the FDA would consider whether to require manufacturers to make labelling changes and conduct post-marketing studies to clarify the risk. The FDA was not involved in the study.
The FDA has warned that one popular depression drug, Paxil, from GlaxoSmithKline, may increase the risk of rare heart problems in newborns exposed to the medication in uteri.
"We do not know for certain that the drugs actually caused persistent pulmonary hypertension, and that if they did, the risk is still low, about one in a hundred. But women should be informed," said the new study's lead author, Dr. Christine Chambers, an assistant professor of paediatrics at the University of California, San Diego, who worked with researchers from Boston University and Harvard.
Psychiatrists estimate that 10 per cent to 15 per cent of pregnant women suffer bouts of depression, and at least 1 in 10 of those take antidepressants.
Between 1998 and 2003, the research team interviewed 377 women who had recently given birth to a baby with persistent pulmonary hypertension. The researchers found that 3.7 per cent of the infants had been exposed to commonly prescribed antidepressants after the 20th week of pregnancy, about six times the rate among infants in a comparison group of healthy babies born at the same time, state media reports
According to the researchers, who conducted this study drugs may hinder the body's production of agents that help blood vessels dilate. If the vessels in a newborn's lungs do not open properly, they cannot absorb sufficient oxygen, and the body may reflexively hold its breath, further starving itself of air, doctors say. Giving an infant oxygen, or nitric oxide, which helps open vessels, often relieves the problem. An estimated 10 per cent to 20 per cent of cases are severe enough that doctors may connect an affected child to an artificial lung.
The antidepressants belong to a class of drugs that acts in the brain to prolong the action of a mood-related messenger chemical called serotonin. They included Celexa, from Forest Laboratories; Zoloft, from Pfizer; Paxil; and Prozac, from Eli Lilly.