By John Tozzi

Prozac, Paxil, Zoloft, and their generics are among the most commonly prescribed antidepressants in the U.S. Research now suggests taking them during pregnancy may increase the chances your child will have autism.

Autism spectrum disorder—a developmental condition characterized by trouble communicating and speaking—is estimated to affect 1.5 percent to 2 percent of U.S. children, depending on how it's measured, according to the Centers for Disease Control. Meanwhile, about 11 percent of Americans over the age of 12 take antidepressants, according to the latest data from the CDC.

A recent study lends insight into one factor that may influence rising rates of autism spectrum disorder, including Asperger syndrome. Only a few other studies have examined links to antidepressants and pregnancy—the latest from the University of Montreal is the largest of its kind.

Researchers analyzed provincial health records of more than 145,000 pregnancies and births in Quebec from 1998 to 2009. Children with autism were found to be born more often to mothers who took antidepressants than to those who didn't. While the study offers no definitive answers, the effect persisted when researchers sought to adjust for the possibility that depression itself raised the risk. Psychiatric disorders, both during pregnancy and after birth, have been linked to other developmental problems.

Scientists don't fully understand the causes of autism, though many suspect a mix of genetics and environmental factors. Trying to gauge the role of medications during pregnancy is difficult—experts cautioned that there isn't any clear evidence that allowing depression to continue untreated is safer than taking antidepressants.

“There’s no good study design to tease those apart,” said Siobhan Dolan, a professor of clinical obstetrics and gynecology at the Albert Einstein College of Medicine who isn't involved in the study. “It’s not, ‘medication is bad and being a depressed mother is a perfectly fine outcome.’ There’s an impact of having depression and trying to raise a child."

Bryan H. King, a psychiatrist at Seattle Children's Hospital, wrote, regarding the study, that further research is unlikely to reveal "a straight line" between the use of antidepressants during pregnancy and autism. Also, the Quebec study wasn't a randomized control trial, the gold standard for establishing the effects of a particular drug. Instead, it looked at medical records retrospectively, which means that unforeseen factors could account for any link between antidepressant use and autism.

Still, the authors said women who took a common class of antidepressants known as selective serotonin reuptake inhibitors, or SSRIs, during the second and third trimesters were more than twice as likely than other women to have children who later developed autism.

The overall likelihood of a child developing autism remains small. If taking antidepressants during pregnancy were to double the risk of a child developing autism, “it means going from 1 percent to 2 percent," says Anick Bérard, a co-author of the study and professor of pharmacy at the University of Montreal.

Bérard says women with mild or moderate depression may want to consider non drug approaches, such as therapy or exercise, that have been shown to alleviate symptoms. “What we’re trying to do with this study is basically to give data to women,” she says. “I’m not trying to scare women, but women need to be aware of the risks and benefits of what they’re doing."

Pfizer, the maker of Zoloft, hasn't identified autism as a safety risk of taking the drug during pregnancy, company spokesman MacKay Jimeson said in an e-mail. "There is extensive science supporting the safety and efficacy of sertraline," he wrote, using the drug's generic name.

Sarah Spencer, a spokeswoman for GlaxoSmithKline, developer of Paxil, said doctors should advise women before prescribing antidepressants, ``recognizing that for some the benefits of therapy may continue to outweigh the potential risks."