DEAR DOCTOR K: My sister recently gave birth prematurely, at 33 weeks. Thankfully, the doctors think my new niece will do well and should not have developmental problems. I know that doctors are able to save more premature babies these days than they used to. What determines whether a "preemie" survives?
DEAR READER: I'm glad to hear that your new niece is doing well. Being born at 33 weeks means she was born seven weeks early. Most babies are delivered about 40 weeks after the mother's last menstrual period. Labor starts with a perfectly timed cascade of hormonal signals between the developing fetus and the mother. Contractions develop, the cervix dilates, and before long, out comes a well-developed, healthy newborn. But sometimes labor comes early.