Researchers: High Cholesterol Is Risk Factor for Preeclampsia

October 07, 1999

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Elevated cholesterol levels appear to be a risk factor for preeclampsia, a team of Harvard researchers has found.

Preeclampsia is a serious condition in which high blood pressure, fluid retention, and protein in the urine anger both mother and child during the second half of pregnancy.

"This may prove to be one of the few controllable risk factors for preeclampsia, a disorder for which we have no treatment and one that affects thousands of women every year," says Ravi Thadhani, an instructor in medicine at Harvard Medical School. "We

need to learn more about exactly which lipids are involved in this

observation, but it's a first step toward developing effective prevention techniques."

Much remains unknown about the ultimate cause of preeclampsia. If not appropriately managed, a woman with

preeclampsia can proceed to eclampsia – characterized by seizures – or liver or kidney failure. Any of these complications can prove fatal.

Preeclampsia also increases the risk of premature delivery, or may make it necessary to perform an emergency cesarean because delivery is the only cure for the condition. In such instances, the baby faces numerous risks associated with prematurity.

It is estimated that preeclampsia occurs in 5 percent of pregnancies and is more common in women having their first

pregnancy. While preexisting diabetes and high blood pressure have been identified as risk factors, standard treatments for those conditions have not been effective in reducing the risk.

"We wanted to look at factors that could be modified before pregnancy and may play an important role in the disorder," says Thadhani. "Other studies have shown that obese women have two or three times the risk of developing hypertensive disorders of pregnancy – a category that includes preeclampsia. Since obesity can be associated with a number of metabolic changes, including increases in blood fats like cholesterol and triglycerides, we examined more closely the role of obesity and elevated

blood fats in both preeclampsia and gestational hypertension."

The research team identified almost 16,000 women participating in the Nurses’ Health Study II who reported at least one pregnancy between 1991 and 1995. Women who had reported either gestational hypertension or preeclampsia in the study’s regular surveys taken in 1993 and 1995 were sent a questionnaire to

confirm their earlier report and request permission to review their medical records. Permission was received and adequate medical records acquired for more than 600 women. Of those, 216 had confirmed gestational hypertension and 86 had confirmed preeclampsia.

Information on those two groups was compared

with data on the almost 15,000 women in the original sample

not reporting any hypertensive disorder of pregnancy. The researchers found a strong association between elevated cholesterol and preeclampsia. Of the 86 women who had preeclampsia, 22 percent reported having elevated cholesterol levels before pregnancy, compared with only 11 percent of those with gestational hypertension or in the control group.

Thadhani notes that this result supports and is supported by a British study that "suggested that Vitamins C and E may reduce the risk of preeclampsia in women at high risk for the disorder, probably because they are antioxidants. That meshes nicely with our result associating elevated cholesterol with preeclampsia, because cholesterol contributes to oxidative stress – damage to blood vessels caused when fats are oxidized and release harmful molecules called free radicals."

More knowledge is needed, however, to devise treatments to reduce this cholesterol-associated risk, Thadhani added. "The information in Nurses’ Health Study II only indicates elevated overall cholesterol, it doesn’t break it down into components like LDL ["bad cholesterol"] and triglycerides. Future studies need to confirm our findings and better define what specific lipids are involved, which will give us targets for prevention. Until then, we can say that pregnant women who have elevated cholesterol before their pregnancies, and other risk factors like first pregnancy, diabetes, and preexisting hypertension, should be followed more closely by their obstetrician.

"At the moment," he continues, "there is a debate among physicians as to the usefulness of checking cholesterol levels in young women. This study certainly suggests a possible reason for doing so, but more work is needed before guidelines should be changed."

This report appears in the October issue of Obstetrics and Gynecology. The Nurses’ Health Study II is based at the Harvard School of Public Health and Brigham and Woman’s Hospital in Boston. Initiated in 1989 in connection with the Nurses’ Health study that began in 1976, it is the longest major women’s health study ever undertaken.