NUMBER OF PREGNANCIES AND THE SUBSEQUENT RISK OF CARDIOVASCULAR-DISEASE

Background. Whether increasing parity or gravidity is a risk factor fo r coronary heart disease has been debated, but the question remains un resolved. Methods. We tested the association between the number of pre gnancies and a variety of cardiovascular end points in two groups of w omen who had completed childbearing. One group comprised 2357 women wh o were followed for 28 years through the Framingham Heart Study, and t he other 2533 women followed for at least 12 years through the first N ational Health and Nutrition Examination Survey National Epidemiologic Follow-up Study (NHEFS). Results. The rates of coronary heart disease were higher among multigravid women than among women who had never be en pregnant, in both the Framingham Heart Study and the NHEFS, but in both studies, the higher rates were statistically significant only in women with six or more pregnancies. For the women in the Framingham St udy, the rate ratio adjusted for age and educational level in the grou p with six or more pregnancies (as compared with women who had never b een pregnant) was 1.6 (95 percent confidence interval, 1.1 to 2.2). Fo r the women in the NHEFS, the same adjusted rate ratio was 1.5 (95 per cent confidence interval, 1.1 to 1.9). Adjustments for other known car diovascular risk factors, including weight, did not markedly alter thi s risk. The rate of total cardiovascular disease was also significantl y higher among multigravid women in the Framingham Study than in the w omen who had never been pregnant. Conclusions. In two prospective Amer ican studies, having six or more pregnancies was associated with a sma ll but consistent increase in the risk of coronary heart disease and c ardiovascular disease. Whether gravidity itself or some other unmeasur ed factor accounts for the increase in risk that we observed requires further investigation.