More and More Babies Born Too Soon
Early Delivery: 'A Problem We Should Have Solved' continued...
"With all of our new toys and equipment, and with all of our new leaps in gene research, we still don't know how to keep women from delivering early," says epidemiologist Claudia Holzman, PhD, of Michigan State University. "The big story isn't that preterm deliveries are on the increase, it is that we haven't solved the problems that cause them."
"The fact is, this is a problem we should have solved, but we are still grappling with it," echoes the March of Dimes' Mattison.
Holzman and MSU colleagues are evaluating sources of stress and responses to it in a group of 1,500 women being followed from midpregnancy. The researchers are studying stress-related responses such as blood pressure, heart rate, and hormone levels.
Hormones released in response to stress may make blood vessels narrow, causing damage to the placenta and prompting premature delivery. Stress responses may also damage the immune system, promoting uterine infections implicated in premature delivery. And stress is believed to boost production of a hormone -- called corticotropin-releasing hormone -- that is thought to play a role in triggering labor.
"Some studies suggest that if a woman is abused or neglected early in life, she may be hypersensitive to stress," Holzman says. "She may put out more stress hormones, which can affect pregnancy."
Savitz, who is chairman of the department of epidemiology at the University of North Carolina, Chapel Hill, is principal investigator for the ongoing Pregnancy, Infection, and Nutrition study, one of the largest and most comprehensive studies to date exploring the potential causes of preterm delivery. Researchers are currently looking at data gathered from 3,000 women and hope to enroll another 2,000 in the study, which examines social, economic, nutritional, and biologic factors possibly related to premature births.
So far, Savitz says, the researchers have found no previously unidentified factors responsible for premature delivery. In fact, analysis of preliminary data suggest that several behaviors thought to be associated with preterm delivery -- like smoking cigarettes and using cocaine -- may not be.
"Obviously, both of these things play a big role in fetal development, but our findings suggest they don't influence delivery," Savitz says. "There are a lot of hypotheses and very little clear data on what the relevant risk factors for preterm birth are. I wish I could tell you we have some striking new evidence of what causes this, but so far we are finding more things that aren't related."