Absent dads linked to early sex by daughters. (Where's Poppa?).

Teenage girls in the United States and New Zealand show a particularly strong tendency to engage in sexual activity and to get pregnant if they grew up in families without a father present, a new long-term study finds.

"These findings may support social policies that encourage fathers to form and remain in families with their children, unless the marriage is highly [conflicted] or violent," conclude psychologist Bruce J. Ellis of the University of Canterbury in New Zealand and his coworkers in the May/June Child Development.

Prior studies have shown early sexual activity and teenage pregnancy among girls who grow up from infancy without a father. However, scientists have generally assumed that precocious sexuality results from a mix of adverse influences, including a father's absence, divorce, poverty, and the lack of parental guidance.

For their new analysis, the investigators studied 242 girls living in one of three U.S. cities and 520 girls living in Christchurch, New Zealand. Participants were interviewed annually from age 5 to 18, and their mothers were interviewed each year.

Among the U.S. girls, a father's absence was associated with his daughter's sexual activity before age 16 and teenage pregnancy regardless of other adversities, Ellis' group reports. In New Zealand, additional problems showed a modest correlation with the girls' sexual activity.

In both countries, rates of teenage pregnancy were highest among girls who had lived in single-parent homes the longest. The teen pregnancy rate was nearly 8 times as high among girls who were no more than 5 years old when their fathers departed as among girls in two-parent families. The pregnancy rate among girls who were between 6 and 13 years old when their fathers left was about 3 times that of two-parent teens.

In the United States, absent fathers were associated only with girls' early sexual activity and teenage pregnancy and not with other behavioral, emotional, or academic problems, the researchers say. In New Zealand, girls who grew up without fathers also exhibited relatively high rates of delinquency and school troubles.

"It's surprising to find such a specific relationship between absent fathers and girls' later sexual behavior," comments psychologist Sara R. Jaffee of the Institute of Psychiatry in London. A father's presence doesn't always serve children well, she says. In the Jan./Feb. Child Development, a team led by Jaffee reported that, at age 5, boys and girls in two-parent families with impulsive, irritable, and often violent fathers exhibit more behavioral problems than do children living only with their mothers. That study took place in England and Wales.

Ellis is examining two possible causes of his provocative correlation. Girls who see their single mothers date many partners may become primed for early sexual exploration. Or, a father's absence early in life may trigger doubts in girls about male reliability that hasten sexual activity and reproduction, as well as promote a preference for brief relationships.