Women who stay active early in pregnancy may have lower cholesterol than those who take it easy, new research suggests.

Investigators found that among 925 pregnant women evaluated at the end of the first trimester, levels of total cholesterol and blood fats called triglycerides declined as exercise levels increased.

It is normal for a woman’s cholesterol and triglycerides to go up during pregnancy, lead study author Carole L. Butler told Reuters Health, but particularly large increases have been linked to the pregnancy complications gestational diabetes and preeclampsia - a potential dangerous condition marked by high blood pressure, fluid retention and protein in the urine.

Some studies have found evidence that exercise lowers a woman’s risk of both of these complications. The new findings suggest that effects on cholesterol could be one reason, said Butler, a researcher at the University of Washington in Seattle.

She and her colleagues report the findings in the American Journal of Epidemiology.

The study included women who were interviewed around their 13th week of pregnancy about their exercise habits over the previous week, as well as other lifestyle and health factors. The researchers found that women who spent the most time being active - about 13 or more hours a week - had the lowest total cholesterol and triglyceride levels, while sedentary women had the highest. More moderate exercisers fell somewhere in between.

Similarly, women who reported vigorous activities such as jogging had lower cholesterol and triglycerides than women who engaged in moderate exercise such as “casual” swimming and biking. Again, sedentary women had the highest levels.

However, it seems a woman need not exercise intensely to see the most cholesterol benefits. According to Butler, time spent exercising, whatever the activity, was just as strongly related to cholesterol levels as exercise intensity was.

She said the findings should encourage research into the effects of exercise later in pregnancy as well.

SOURCE: American Journal of Epidemiology, August 15, 2004.