New research is uncovering genetic links that may help explain some of the mystifying premature births among women who start pregnancy with no known risk factors.
Working separately, Dr. Jerome F. Strauss III, dean of the Virginia Commonwealth University's School of Medicine, and Dr. Xiaobin Wang, at Children's Memorial Hospital in Chicago, Illinois, found two different inherited traits that can help predict the risk of premature birth. The March of Dimes supported both researchers' work through its Prematurity Research grants, which total more than $4 million.
More than a half million babies are born too soon each year and the preterm birth rate has increased more than 30 percent since 1981. Babies who do survive face risks of lifelong challenges of cerebral palsy, mental retardation, chronic lung disease, and vision and hearing loss, as well as other developmental problems.
While there are several factors that can help predict the risk of preterm birth, there is no known cause for half the cases, leading researchers to focus on inherited genetic makers.
A recent Institute of Medicine report documented the growing problem of premature birth and outlined the need for expanded research to understand the roles of genetic susceptibility and gene-environment interactions in preterm birth. Experts believe that understanding these factors could lead to major improvements in the diagnosis, prevention, and treatment of preterm birth.
Dr. Strauss found that African American babies are three times more likely than babies of European descent to have genetic variation of the SERPINH1 gene that caused it to produce a reduced amount of the protein, collagen, which may lead to weakened fetal membranes, also called the "bag of waters." Because the membranes are weakened, there is an increased chance of premature rupture of the membranes and premature birth.
African Americans had an average premature birth rate of 17.6 for 2001-2003, above the national rate of 12.1, and the highest of all the racial groups.
Dr. Strauss' work, "A Functional SNP in the Promoter of the SERPINH1 Gene Increases Risk of Preterm Premature Rupture of Membrane in African Americans" was published online and will appear in a future issue of the Proceedings of the National Academy of Sciences.
"This is an example of how heredity may play a role in pregnancy complications and how genetic factors can contribute to racial disparities in the incidence of preterm birth," said Dr. Strauss. "With better understanding of this genetic variation, we hope to be able to identify pregnancies at greater risk of preterm birth and intervene to prevent it."
"Supporting research is critical if we are to end this epidemic," said Dr. Nancy Green, medical director of the March of Dimes. "While findings like those of Dr. Wang and Dr. Strauss are not a magic bullet that will cure prematurity, they are crucial to our fight."
Dr. Wang's research found that a genetic variant of the Prolylcarboxypeptidase gene had a significant association with preeclampsia, characterized by high blood pressure and high levels of protein in the urine, which can develop by the 20th week of pregnancy. The only known cure for preeclampsia is delivery of the baby, often prematurely. Women who have the gene variant, and had chronic hypertension before becoming pregnant, had the greatest risk of developing preeclampsia.
"This genetic association could be a highly sensitive and specific early predictor of preeclampsia among women with chronic high blood pressure even before pregnancy," said Dr. Wang.
Her work, "Prolylcarboxypeptidase Gene, Chronic Hypertension, and Risk of Preeclampsia," was published in Vol. 195, No. 1 of the American Journal of Obstetrics and Gynecology.
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