A course of antibiotics during pregnancy thankfully won’t bring any immediate harm to your child, according to new research published Friday in the journal Pharmacoepidemiology and Drug Safety.

The study authors analyzed data that was collected through the Quebec Pregnancy Cohort, a population-based study of Canadian mothers and their newborns that recorded the mothers' "lifestyle [and] socioeconomic risk factors, use of natural products and over-the-counter medications, and pregnancy history."

That level of detail allowed the current researchers to key in on any connections between the use of two antibiotics, azithromycin and clarithromycin, during pregnancy and the rate of later congenital defects. Both antibiotics belong to a class of drugs known as macrolides.

"With penicillin, macrolides are amongst the most used medications in the general population and in pregnancy. However, debate remained on whether it is the infections or in fact the macrolides used to treat them that put women and their unborn child at greater risk of adverse pregnancy outcomes, including birth defects," elaborated study author Dr. Anick Bérard, of the University of Montreal, in a statement. "We therefore aimed to estimate the risk of major congenital malformations after [fetal] exposure to the two most commonly used macrolides, and failed to find any."

Because penicillin is known to interact well with pregnant women, Bérard and her team decided to compare the rate of defects in both penicillin- and macrolide-using expectant mothers, ultimately studying 135,839 pregnancies. "Of these, 1.7 percent involved exposure to the macrolides during the first trimester, while 9.8 percent of pregnancies resulted in the child having a major congenital malformation. After statistical analysis, we found no meaningful association between the groups compared to penicillin use," explained Bérard and her co-author Professor Hedvig Nordeng, of the University of Oslo.

As alluded to by Bérard, the diseases that azithromycin and clarithromycin are used to treat, such as chlamydia, can sometimes have a negative impact on the health of the child, so it’s been difficult to tease apart the relationship between antibiotics and birth defects. And while these drugs represent the most commonly used antibiotics, the authors caution that more research needs to be conducted on other types as well.

In addition, while the short term impact of maternal antibiotics on a newborn may be limited or negligible, a 2014 study found the use of antibiotics in the second or third trimester of pregnancy increased the risk of childhood obesity by 84 percent compared to those whose mothers didn’t use antibiotics. Of course, no one study is the final word on anything, but it does suggest more research on the risks and benefits that prenatal antibiotics offer both mother and child should take place.

Source: Bérard A, Sheehy O, Zhao J-P, et al. Use of macrolides during pregnancy and the risk of birth defects: a population-based study. Pharmacoepidemiology and Drug Safety. 2015.