Research published Monday by the journal JAMA Pediatrics found that a woman’s use of acetaminophen at 18 and 32 weeks of pregnancy was associated with greater odds that when the resulting child was 7 years old, his or her mother would report a range of problematic behaviors.

Share story

Acetaminophen, long the mainstay of a pregnant woman’s pain-relief arsenal, has been linked to behavioral problems in children born to mothers who used it during pregnancy.

Research published Monday by the journal JAMA Pediatrics found that a woman’s use of acetaminophen — the active ingredient in Tylenol — at 18 and 32 weeks of pregnancy was associated with greater odds that when the resulting child was 7 years old, his or her mother would report certain problematic behaviors.

Compared to women who reported no acetaminophen use at 18 weeks of pregnancy, those who took the medication at that point of gestation were 42 percent more likely to report hyperactivity and 31 percent more likely to report conduct problems in the children they bore.

Women who took acetaminophen at 32 weeks of pregnancy were 29 percent more likely to report emotional difficulties in their child at age 7. Children born to mothers who took acetaminophen late in their pregnancy were 46 percent more likely to experience a wide range of behavioral difficulties than were children born to moms who took no acetaminophen at that point.

Finding a link between acetaminophen use during pregnancy and an outcome affecting the child is no proof that acetaminophen is the cause of the outcome. But the authors contend that the study results do heighten concerns that fetal exposure to acetaminophen can give rise to neurodevelopmental problems.

Several epidemiological studies have linked acetaminophen use during pregnancy to ADHD-like behaviors in the child.

Research performed on mice has suggested that the medication alters brain development by disrupting hormonal function in the developing fetus. And several other mechanisms of injury also have been suggested.

The authors of the study took several steps to reduce confusion in interpretation of the study’s findings.

They found no link between a child’s behavioral problems at age 7 and his or her mother’s postnatal acetaminophen use, nor any connection to acetaminophen use by the mother’s partner during pregnancy.

The emerging picture points more strongly to a developing fetus’ exposure to acetaminophen as a possible causative factor.

The authors wrote that both the new findings and those of a 2013 study, comparing adverse behavioral outcomes in siblings, suggest that “unmeasured familial factors” — socioeconomic differences, or a mother’s attitudes toward medication use — are not actual causes of a child’s behavioral problems.

The new research also considered genetic factors, but failed to discern a pattern of increased medication-taking by women who were carriers of genetic variations linked to behavioral problems.

The current study asked women when they were pregnant about their medication use, and then — seven years after giving birth — asked them to assess their children’s emotional and social well-being and report a range of problematic behaviors.

The new study reflects the experience of 7,796 mothers who gave birth to a baby in 1991 and 1992 in the county once known as Avon, England.

Acetaminophen has long been seen as safe for use by pregnant women, and more than half of pregnant women in the United States and Europe are thought to use it during pregnancy.

As a fever reducer, acetaminophen is considered a bulwark against a more immediate threat to a developing fetus. The authors cautioned that pregnant women and their physicians should carefully weigh potential harm to offspring against the risks of not treating fever or pain in the mother.