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
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
"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."