What Determines the Timing of Birth?; Women's Health; Scientific American Presents; by Brown; 1 Page(s)

Babies arrive unannounced. Some show up three weeks early. Others appear 10 days past term. Their timing seems random-but it's not. Together the fetus and placenta establish the moment of childbirth by launching a chemical cascade that sets off a mother's contractions. The question is, How does this embryonic duo set the date?

Scientists are now pursuing two main scenarios. According to the first, the placenta runs on a nine-month clock, telling time by the flux of pregnancy hormones. Your clock may run fast, causing an early birth, or slow, bringing a late baby. According to the second, the fetal brain acts like a computer, logging its own growth or the environmental changes until the moment for birth is right. Exploring both ideas, researchers have found telltale hormonal changes that portend premature birth. By picking up on and manipulating these hormonal cues, doctors could one day prevent some babies from being born before their time.