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
Genetics are the most likely reason for the phenomenon, the study’s lead
“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.
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
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.
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.