It’s been known for a while now that using cocaine — no matter the form — during pregnancy is harmful to the unborn fetus. Research linking prenatal cocaine exposure (PCE) to congenital birth defects, low birth weight, and poor development of motor skills has been compelling. Studies have also shown that PCE affects babies mentally and emotionally later in life. New information has emerged linking prenatal cocaine exposure to yet another consequence for the infant as it grows up: early sexual behavior.

Researchers from Case Western Reserve University have been studying mothers — both those who used cocaine during pregnancy and those who did not — to understand the effects of the drug in terms of children’s cognitive and social development. In their latest study, the researchers found a link between PCE and an adolescent’s likelihood to engage in sexual intercourse before the age of 15.

The study looked at the sexual behavior of 354 teens, 180 of whom were exposed prenatally to cocaine, and 174 of whom weren’t. Researchers tested the children at 6, 12 and 18 months, and then again at ages 2, 4, 6, 9 to 12, and 15. The National Institute on Drug abuse funded the study, and will support testing of the children into their 20s.

The results indicated that teens who were prenatally exposed to cocaine were 2.2 times more likely to engage in sexual intercourse by the age of 15 than those who weren’t. The way PCE affects early sexual behavior may differ by gender, said lead researcher Dr. Meeyoung O. Min, assistant research professor of social work at the Jack, Joseph and Morton Mandel School of Applied Social Sciences, in a press release.

Thirty-seven of the PCE teens reported engaging in intercourse as young as 13, and researchers found that greater parental monitoring decreased the likelihood of early sexual intercourse, while exposure to violence increased it. Girls who reported behavior problems during their preteen years were more likely to engage in early intercourse, but no such link was found in boys.

Early engagement in sexual activity has been linked to an increased risk of unplanned pregnancy and sexually transmitted infections, including HIV. The study suggests that interventions targeting externalizing behavior and strengthening parental monitoring may reduce the likelihood of early sexual behavior, and thereby reduce unplanned pregnancy and STDs in PCE teens.

Source: Min M, Minnes S, Lang A, Yoon S, Singer L. “Effects of Prenatal Cocaine Exposure on Early Sexual Behavior: Gender Difference on Externalizing Behavior as a Mediator.” Drug and Alcohol Dependence. 2015.