Millions of soon-to-be mothers trust acetminophen-based painkillers such as Tylenol, but a new study just released has made a concerning find: kids appear to be more likely to develop behavioral problems like hyperactivity when women take acetaminophen while pregnant, at least according to one study.

In a statement from JAMA Network Journals, which published the study, the journal noted that acetaminophen is generally considered safe in pregnancy and is commonly used by pregnant women to combat pain and fever. But it’s the latest study to suggest that acetaminophen may have some effect on the brain development of unborn children.

The findings are based on an analysis of data from 7,796 mothers who were involved in the Avon Longitudinal Study of Parents and Children, which ran between 1991 and 1992. The questionnaires in that study assessed acetaminophen use at 18 and 32 weeks of pregnancy, and when children were 5 years old, with behavior problems in children assessed at 7 years of age.

Study results indicated that there was an increased risk of conduct problems and hyperactivity symptoms in children for mothers who had prenatal use of acetaminophen at 18 and 32 weeks of pregnancy.

The study was limited by a lack of information on dosage, as well as a lack of information on the total duration of acetaminophen use, the statement notes.