"During pregnancy and nursing, hormones cause breast tissue to expand, and the surrounding skin stretches to accommodate this," says Aron Kressel, M.D., chief of plastic surgery at Metropolitan Hospital, in New York City. "Afterwards, the tissue shrinks, but the skin is no longer as elastic." Though the only permanent picker-upper for your postbaby breasts is plastic surgery, you don't have to go under the knife to get a little lift.
What works: Exercise. "Working out won't boost your bra size, because breast tissue is fat, not muscle," says Courtney Barroll, a personal trainer at Equinox Fitness Clubs, in New York City. "But exercise can tone the pectoral muscles around the breasts, giving them a lifted and perkier appearance." Some bust-buffing moves: push-ups (balance on either your knees or, more advanced, your toes elevated on a step or low bench); chest flies lying on your back; pull-overs; and chest presses. However, get your doctor's okay before exercising postpartum.
What doesn't: Breast-firming pills or creams. "There's no evidence they tighten the skin or restore its elasticity," Dr. Kressel says.
Quickest fix: A supportive bra. Be sure to find the right fit -- ask knowledgeable lingerie sales staff for help. Look for a wide band for support, an uplifting underwire, and cups made of sturdy rather than sheer fabric. And to prevent further sagging, wear a sports bra when you work out.