Is there an increased risk of autism spectrum disorders (ASD) in children born to women who took anti-depressant medications late in their pregnancy? A new study suggests the answer may be yes.

But pregnant women shouldn’t chuck their Lexapro prescriptions just yet.

The study, published in the journal JAMA Pediatrics, was conducted using health records of all full-term infants born between 1998 and 2009 in Quebec. By searching a database of information from over 145,000 children for codes used to specify an ASD, researchers identified a little more than 1,000 who had at least one such diagnosis.

Using information about prescriptions mothers were given during their pregnancy, they generated a number known as a hazard ratio to determine if taking an anti-depressant increased the risk of having a child with an ASD.

Their results were striking. They found that children born to women who took an anti-depressant in the second or third trimesters had an 87 percent higher risk of developing an ASD. For those taking one in the class of medication known as selective serotonin reuptake inhibitors (SSRIs), which includes drugs like Prozac and Zoloft (among others), the risk was doubled.

Though maternal depression alone can increase the risk of having a child with an ASD, they found an increased risk of such a diagnosis from taking an anti-depressant even after they controlled for that factor. They did not find an increased risk if the medications were taken in the first trimester.

The authors speculate that, because SSRIs can cross the placenta, they may have a negative effect on brain development at a crucial stage. Certainly, there are other studies that also indicate changes during the later trimesters can have an impact on developing an ASD.

For pregnant women who may be taking one of these medications, reading reports of this new study is probably quite alarming. While there may be some controversy about whether or not there really is an epidemic of ASDs, expectant mothers would likely want to mitigate risk to the degree they can. While the lead author took pains to say in an interview that their goal was not to scare women, many might be scared nonetheless.

However, it’s important to look carefully at this study and think about how much alarm is really called for.

It should be noted that the researchers found nearly 5,000 infants whose mothers took anti-depressants during pregnancy, about 2,500 of whom did so in the later trimesters. Of that number, only 31 infants exposed in utero during that time period developed an ASD. It is statistical analysis of those 31 cases that yields the 87 percent increased risk number.

That is not a lot of cases to be drawing huge conclusions from.

Indeed, only a small reduction in that number has a substantial impact on the conclusion. In a detail tucked behind a paywall within the text of the full study, the authors note that when they restricted their analysis to cases where the diagnosis was confirmed by a psychiatrist or a neurologist, their results were no longer statistically significant. They still found an increased risk of an ASD, but they couldn’t confidently exclude the possibility that the risk was the same as that of the general population.

Does that detail invalidate the whole study? No. But I think it bears mentioning when reporting the findings, especially for such a potentially sensitive topic for many women.

I am neither a psychiatrist nor an obstetrician, and I don’t care for women in the second or third trimesters of pregnancy, depressed or otherwise. I don’t know how or if this new study would affect my practice if I did.

However, I do know that depression during pregnancy can be a serious problem, and I am concerned that women reading articles about this study may be reluctant to seek the care they need because of worry about harming their babies. Obviously, any given patient’s decisions should be made in consultation with a medical provider who knows them, and can help them make the soundest, safest choice.

But this study found thousands of infants whose mothers took medications for depression late into their pregnancies and who did not develop an ASD, and bases its conclusions on a very limited number of children who did. Those facts may not be as eye-catching as some of the headlines it has generated, but they bear notice, too.