Monday, August 21, 2006 (Rueters Health)—A gene variant appears to be one reason why African American women are two to three times more likely than white women to have a premature baby.

The genetic variation apparently reduces the amount of collagen made in the amniotic membranes, which are consequently weaker and more likely to rupture too early, leading to premature delivery.

Previous work has identified a change in one link in the DNA sequence of a gene called SERPIN1 that is associated with premature delivery.

Dr. Jerome F. Strauss, III, from the University of Pennsylvania in Philadelphia and his associates performed DNA analysis for 323 African Americans and 148 European Americans and found the variant form of the gene in 12.4 percent and 4.1 percent, respectively.

According to their report in the Proceedings of the National Academy of Sciences early edition, Strauss and his colleagues then studied 152 newborns from pregnancies complicated by premature rupture of membranes and a comparison group of 174 infants born at term.

The age of the mothers and the number of children they had borne was similar in both groups. The babies in the premature-rupture group had a shorter length of gestation than the term group (31.9 versus 39.1 weeks, on average) and lower birth weights (1937 versus 3309 grams).

Moreover, the SERPIN1 gene variant occurred significantly more often among women whose pregnancies were complicated by premature membrane rupture (11.5 percent) than in mothers with term infants (4.05 percent).

A second similar study resulted in similar findings, making this gene variation "the leading identifiable cause of preterm birth," the authors conclude.

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