WASHINGTON -- As if working mothers didn't have enough to worry about, now comes word that their sons are more likely to lose their virginity at a younger age than teens whose mothers don't work.
A new study estimates that the sons of mothers who worked full-time were 45 percent more likely to have sex at an earlier age than those whose mothers were not working. The odds were 25 percent higher if the mothers worked part-time.
Among blacks, the correlation was even greater: sons of mothers with full-time jobs while they were growing up were 90 percent more likely to have sex earlier than boys of stay-at-home mothers and 55 percent more likely if their mothers worked part-time.
The study, conducted by researchers at the Urban Institute, a Washington think tank, and Wellesley College in Massachusetts, appears in the upcoming issue of Public Health Reports, a journal published by the federal government's U.S. Public Health Service.
Leighton Ku, a public health expert at the Urban Institute who co-authored the study, said he could not explain why sons of working mothers are "at greater risk" of earlier first intercourse than sons of non-working mothers.
But Mr. Ku said the findings suggest that sons of working mothers could benefit from sex-ed programs, perhaps linked with after-school activities. The study found that teen-age boys who were taught about AIDS and ways to say "no" to sex begin to have sex later than other boys.
Kristin Moore, executive director of Child Trends, a Washington research firm that focuses on teen sexuality, said the study should send a message to parents that boys need as much attention as girls.
Supervision, Ms. Moore said, "doesn't just mean watching them every minute but talking to them, explaining risks. There are lots of things that working parents can -- and do -- do to lower the risks for their kids. And that's really the issue. It's not employment per se."
Ms. Moore said it's not just an issue for mothers. "I think we want to ask what are the fathers doing in these families and what could they be doing whether they live in the home or not. They could be doing something to protect their sons. We're beyond the time where there's a clap on the back and 'Way to go.' We're at a point where this is risky."
The study examined the influence of race, family structure, mother's education, employment and other demographic factors on the time a teen-age male first had sex and whether or not a condom or contraceptive was used.
The study was based on the answers 1,880 single males aged 15-19 gave in a federally funded national survey taken in 1988. It also found that males who were held back in school also begin having sex earlier, as did boys whose mothers were teen-agers when they first gave birth.
The study did not look at the father's employment: in many cases, the fathers did not live at home. It also did not examine the sexual history of teen-age females. Earlier studies showed no significant correlation between a mother's employment and when girls first have sex.
Mr. Ku said earlier studies of boys showed some link between mothers working and when boys first have sex, but the new study found "a stronger effect." The study did not specify how much earlier sons of working mothers had sex compared to sons of stay-at-home mothers.
Faced with explosive growth in teen pregnancies, AIDS infection and sexually transmitted diseases among teens, federal health officials say it's critical that teen-agers delay having sex longer for their health and future well-being.
Nearly three-fourths of all high school students say they have sex by the time they graduate. Three million teen-agers -- about one in eight 13-19 year-olds -- acquire a sexually transmitted disease. The United States has the highest rates of teen pregnancy, abortion and childbirth in the industrialized world.
Analysts familiar with the study said they were concerned that working mothers will consider -- wrongly -- that the findings are an attack on them.
"There's so much stress on working mothers and they feel so guilty so often that I think that they might see this and think, 'Oh no, not another thing for which I'm responsible,'" said Ms. Moore.
Researchers said that the reasons some mothers work -- divorce and poverty -- may also be a factor in teen-age boys having sex earlier.
Gary Bauer, president of the conservative Family Research Council in Washington, called the study "another tidbit of evidence that points to a truth we instinctively know but in the '90s don't want to admit: that children do best when they have significant amounts of time with mothers and fathers."
A 1992 survey by the Families and Work Institute, a non-partisan New York research organization, found that stay-at-home mothers spent just under four-and-a-half hours on a typical day with their teen-age children. By contrast, working mothers spent just over two-and-a-half hours with their teens on a typical work day.
"I wouldn't say this proves mothers shouldn't work outside the home," said Mr. Bauer. "I would say the government needs to wake up and start developing policies that make it possible for more families to provide more time with their children." Among the options, Mr. Bauer said, would be lower tax burdens on families with children by raising the personal exemption.