We focus on teen pregnancy so much that we haven’t noticed that some of our tweens -- kids ages 11 to 14 -- are already sexually active. According to a 2009 study published in the Journal of School Health, 12 percent of students reported having sex by age 12. Shocked? Talk to your tween now about sex to give her the information she needs to deal with sexual situations before they happen, says Warren Seigel, M.D., FAAP, FSAHM, Chairman of the Department of Pediatrics and Director of Adolescent Medicine at Coney Island Hospital. While sex education should begin early, it should be appropriate for your tween’s level of understanding, says Seigel. What made sense at age six -- “Babies come from mommy’s tummy” -- will no longer fly with your 11-year-old. She may not want to know everything, either. She may ask you to explain the real biological process of childbirth, but not the mechanics of sex, Seigel says.