October 9, 2007

Low Cholesterol Levels Linked to Premature Birth

Photo of a newborn baby and mother

Low blood cholesterol is usually considered good for your health — but that may not hold true during pregnancy. New findings, although still considered preliminary, suggest that pregnant women with very high or very low cholesterol are more than twice as likely as women with moderate cholesterol levels to deliver their babies prematurely..

Over 12% of births in the U.S. are considered premature, meaning that the baby is born at least 3 weeks shy of a full 40-week pregnancy term. Preterm infants face several health challenges, including breathing difficulties and the potential for lifelong medical problems. Although previous studies had linked high maternal cholesterol to preterm birth, the tie between low cholesterol and premature delivery had not yet been reported.

In the new study, published in the October 2007 issue of the journal Pediatrics, a team of scientists analyzed medical information for 1,058 healthy pregnant women and their newborns. The women were between 21 and 34 years old and had been referred to medical clinics in South Carolina for routine prenatal care. The researchers limited their study to women who were nonsmokers and who did not have diabetes or certain other medical conditions. Blood cholesterol levels were assessed from their second trimester of pregnancy.

The research team — including scientists from NIH's National Human Genome Research Institute (NHGRI) and the NIH Clinical Center — found that nearly 13% of the women with very low cholesterol gave birth prematurely, compared with 5% of those within the moderate range (159-261 milligrams per deciliter). As in previous studies, the scientists also found that about 12% of women with very high cholesterol had preterm deliveries.

When the scientists looked separately at data from Caucasian and African American women, they found that black women with very low cholesterol did not seem to be at greater risk for preterm birth. In contrast, almost 21% of white women with the lowest cholesterol levels had preterm deliveries. The reason for these differences is unknown.

Low cholesterol also may affect birth weight, regardless of race. For both racial groups, when babies were delivered at term, mothers with very low cholesterol had newborns weighing 5 ounces less on average than babies delivered to women with moderate cholesterol.

"Based on our initial findings, it appears that too little cholesterol may be as bad as too much cholesterol during pregnancy, but it is too early to extrapolate these results to the general population. More research is needed to replicate this outcome and to extend it to other groups," says Dr. Max Muenke, the study's senior author and chief of NHGRI's Medical Genetics Branch. "For now, the best advice for pregnant women is to follow the guidance of their health care providers when it comes to diet and exercise."

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