Teenage girls commonly have sex not because they want to, but because they feel pressured into it - and the result may be a higher risk of sexually transmitted diseases and pregnancy, a new study suggests. Researchers found that among 279 teenage girls they interviewed, many said they'd given in to unwanted sex at some point because they were afraid their boyfriend would get angry. The findings, published in the Archives of Pediatrics & Adolescent Medicine, indicate that may teenagers -- both female and male -- need help in negotiating their relationships. "We need to give guidance to teens on...