Black women are three times more likely than white women to deliver their
babies prematurely, a new study reveals. Even worse, they are four times more
likely to give birth extremely prematurely — between 20 to 28 weeks
gestation.
Genetics are the most likely reason for the phenomenon, the study’s lead
researcher said.
“It has been known that African-American women have an increased risk of
preterm delivery,” said Dr. Louis J. Muglia, director of the Center for Preterm
Birth Research at Washington University School of Medicine, in St. Louis. “By
this study we are trying to understand the foundation for that effect.”
His team published its findings in the February issue of the American
Journal of Obstetrics and Gynecology.
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The study tracked more than 700,000 births in Missouri from 1989 to 1997.
The researchers found that black women were three times more likely than
their white counterparts to give birth at 20 to 34 weeks of pregnancy, rather
than full-term (from 37 to 41 weeks).
The researchers controlled for socioeconomic factors, such as maternal age
and economic status, Muglia said. Without adjusting for those factors, “the
incidence of premature delivery would be 6.5-fold higher than in Caucasians,” he
noted.
In addition, 21.5 percent of the black women in the study had more than one
premature delivery, compared to 9.2 percent of white women, the study found.
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While there is no direct proof that genetic differences drive the disparity,
the evidence does point in that direction, Muglia said. His group now is engaged
in studies to try to prove that notion, he added.
“What we would like to do is identify in a broad way the factors that
increase the incidence of premature delivery,” Muglia said. “We want to identify
families and examine them for polymorphisms,” genetic differences associated
with an increased incidence of premature childbirth.
Muglia and his colleagues have been working with 75 families in the St. Louis
area for the past three years, and have started a study of similar families in
Finland. “We don’t have data yet,” he said. “It would take many subjects to pick
out those genes.”
One working hypothesis is that there might be some hidden evolutionary
benefit to preterm delivery. “For maternal survival, it might be better to
deliver early,” Muglia theorized.
To support that notion he cited sickle cell anemia, a genetic condition more
common in blacks than whites. Carriers of two genes for the condition are at a
handicap, but it has been found that the presence of a single sickle cell gene
protects the carrier against malaria, Muglia noted.
“I’m not sure it really gives us definitive answers,” said Dr. Diane Ashton,
deputy medical director of the March of Dimes. “But it is one aspect that the
March of Dimes is looking at to assess the differences in premature births.”
There have been hints of a genetic factor, Ashton added, citing a study
indicating that black women were more susceptible to early rupture of the
membranes.
“There is some evidence here, but this is one study, and until we have some
reproducible results I don’t think we can base our final opinion on just one
study,” she said.
A 2006 report by the U.S. Institute of Medicine found that 12.5 percent of
American babies were born at least three weeks ahead of their full-term delivery
date. Care for those babies costs the nation $26 billion a year, with some
requiring neonatal intensive care for two weeks.
Potential problems for premature babies include hearing loss, vision loss,
cerebral palsy and seizures. Such problems are most common in babies born before
32 weeks of pregnancy.
More information
For more on premature babies, consult the March of Dimes.
By Ed Edelson
HealthDay Reporter
SOURCES: Louis J. Muglia, M.D., Ph.D, director, Washington University Center
for Preterm Birth Research, St. Louis; Diane Ashton, M.D., deputy medical
director, March of Dimes; February 2007 American Journal of Obstetrics and
Gynecology
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