Women with very low cholesterol levels early in pregnancy may be at increased risk for giving birth prematurely, and for delivering infants with lower birth weights than women with moderate cholesterol readings.
The surprising findings also suggest preterm births associated with low cholesterol may be linked to race, with white women having four times the risk of black women with similarly low cholesterol.
In the study, researchers measured cholesterol levels in routinely collected prenatal blood samples from more than 1,000 women ages 21 to 34. The women were from white or black ethnic backgrounds and did not have other risk factors for pregnancy complications, such as a twin pregnancy, a smoking habit or diabetes.
The preterm birth rate was five per cent in women with moderate cholesterol levels, 12 per cent in women with high cholesterol and 13 per cent in women with low cholesterol. While researchers had expected to find a higher incidence of preterm birth in women with high cholesterol, they were surprised to find similar results in women with low cholesterol, says Dr. Maximilian Muenke, the senior study author and chief of medical genetics at the National Human Genome Research Institute in Bethesda, Md.
“We were even more surprised when we … looked at their ethnic background, and we found African-American women who have low cholesterol had about the same prematurity rate as those women in the moderate range: about five per cent,” he says. “In those women with low cholesterol, we found white women had a prematurity rate of 21 per cent. That was four times higher, and that was surprising to us. Very, very surprising.”
However, one area in which black and white women with low cholesterol had similar findings was in birth weights for term infants: They were more likely to have term infants who weighed significantly less (by about 150 grams) than those born to mothers with moderate cholesterol levels.
Muenke says cholesterol is known to play important roles in fetal development throughout pregnancy. “In essence, growth is not possible without cholesterol.”