New York, July 10 (IANS): Teenagers whose mothers used cocaine while pregnant are much likely to have sexual intercourse before age 15, a study says.

The study found that teenagers who were prenatally cocaine exposed (PCE) were 2.2 times more likely to engage in sexual intercourse before age 15 than those who were not.

Yet how PCE affects early sexual behaviour may differ by gender, said lead researcher Meeyoung O. Min from Case Western Reserve University, US.

Researchers studied mothers - some who used cocaine while pregnant and others who did not - since 1994 to understand how the drug affected their children's cognitive and social development.

The new study focused on sexual activities of 354 adolescents (180 prenatally exposed to cocaine and 174 who were not).

Researchers tested the children at 6, 12 and 18 months, and at ages 2, 4, 6, 9 through 12 and 15.

Compared to 23 percent of non-cocaine exposed (NCE) teenagers, 29 percent of prenatally cocaine exposed (PCE) teenagers living in foster/adoptive care and 42 percent of PCE teenagers living with their birth mothers reported having sexual intercourse before age 15.

Cocaine-exposed teenage girls who reported having behaviour problems during their preteen years were more likely to have early sexual intercourse.

As many as 64 youth (37 PCE and 27 NCE) reported having sex as young as 13. Levels of lead in the blood during preschool years was also related to a greater likelihood of early sexual intercourse.

Greater parental monitoring decreased the likelihood of early sexual intercourse, while exposure to violence increased the risk, the study found.

Early sexual engagement has been associated with an increased risk of unintended teen pregnancies and sexually transmitted infections, including HIV.

Substantial research has documented that childhood behaviour problems (aggression, antisocial behaviour, delinquency) may be a precursor of sexual engagement at an early age.