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Preterm Birth Study Probes Role of Genetics, Nutrition and Race

PITTSBURGH, November 28, 2006 — A recent study from the U.S. Centers for Disease Control and Prevention found that preterm birth contributed to more than a third of infant deaths – twice as many as previously thought, making it the leading cause of infant deaths – yet the underlying causes of premature birth are not well understood. A new investigation by researchers at the University of Pittsburgh-affiliated Magee-Womens Research Institute (MWRI) is the first to address the interactions of genetic and environmental factors such as nutrition and inflammation that may figure in the racial disparity in preterm birth, or birth prior to 37 weeks gestation.

The U.S. infant mortality rate has declined since 1995 except between 2001 and 2002, when the rate increased for the first time since 1958. In 2002, the National Center for Health Statistics listed short gestation or low birth weight as the cause of 17 percent of infant deaths. However, two-thirds of the infants who died in 2002 were born prematurely.

Considering that infant mortality rates in Pittsburgh and Allegheny County have for years exceeded those of other major U.S. cities, this study is of particular interest locally. In 2002, the overall infant-mortality rate in the county was eight per 1,000 births, compared to the national rate of five per 1,000 – itself high among industrialized nations. According to the Allegheny County Health Department, in 2002, the infant-mortality rate for blacks was more than 4.5 times higher than that for whites. In Pittsburgh, the rate for blacks was 2.9 times higher than that for whites, meaning that black infants are the highest risk group for infant mortality.

In addition, Allegheny County Health Department statistics for the year 2000 note that one in 12 births countywide represented a baby of low birth weight (5 pounds, 8 ounces), and one in 55 births represents a baby of very low birth weight (3 pounds, 5 ounces). Such infants are at much higher risk for serious medical problems and death.

Year 2000 statistics also show that blacks had a 2.2 times greater likelihood of being low birth weight and a three times greater likelihood of being very low birth weight than did whites. Among black newborns, 14.3 percent were low weight and 3.9 percent were very low weight. Among whites, 6.6 percent were low weight and 1.3 percent were very low weight.

More than 500,000 babies are born too soon each year, and the preterm birth rate has increased more than 30 percent since 1981. Babies who do survive may face risks of lifelong challenges related to cerebral palsy, intellectual disability, chronic lung disease, or vision and hearing loss, as well as other developmental problems.

“Preterm birth is a complex condition, and this in-depth study of nutritional status and genetics is unique,” says Hyagriv Simhan, M.D., M.S.C.R., assistant professor of obstetrics, gynecology and reproductive sciences at the University of Pittsburgh School of Medicine and principal investigator for the study. “Nutrition is something that lends itself to interventions to improve health. For example, we now know that women who take folic acid before conception and during pregnancy can reduce the risk of spina bifida and other neural tube defects by as much as 70 percent.”

The five-year, $2.8 million study funded by the National Institute of Child Health and Human Development will enroll 1,200 participants early in pregnancy to discern the interrelationship of dietary factors, genetics and infection-related inflammatory changes in the lower genital tract that are known to predispose women to preterm birth.

The study aims to determine whether poor nutrition before conception and during pregnancy is associated with an increased risk for preterm birth, how nutritional status affects the risk of genital tract inflammation and the roles of genetic mutations and race, which may predispose women to infection.

“We know, for instance, that African-American women are much more likely than white women to have genetic mutations that are associated with infection-related preterm birth,” said Dr. Simhan, who also is an assistant investigator at MWRI and director of the Prematurity Center at Magee-Womens Hospital of the University of Pittsburgh Medical Center.

Compared with white women during pregnancy, African-American women report higher intakes of calories, fat and vitamin C, while white women consume increased amounts of protein, folate and fiber. Overall, Dr. Simhan speculates, white women may have a more nutrient-rich diet. African-American women are more likely than white women to have third-trimester anemia (42 percent compared to 24 percent) and iron deficiency (15 percent versus 10 percent). During their childbearing years, some 42 percent of African-American women suffer vitamin D deficiency, compared with 4 percent of white women. Blacks also are more likely than whites to gain inadequate weight during pregnancy, Dr. Simhan notes.

Study participants will be asked to provide investigators with information about their diet, body-mass indices and weight gains during pregnancy. In addition, blood and nail samples will be analyzed for an objective reflection of nutritional status.

“Understanding the influence of environment and gene-environment interactions on inflammation is critical to understanding the racial disparity in preterm birth,” says Dr. Simhan.

For further information about the study, call 412-641-4085.

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