Serum lipids in young women before, during, and after pregnancy.

The associations between pregnancy and serum lipids were investigated in a cohort of 831 Dutch women, initially aged 5-19 years. These women were examined yearly from 1975 to 1985 for an average period of six years, as part of a longitudinal survey of risk factors for coronary heart disease. During this period, 62 women became pregnant, and their serum total and high density lipoprotein (HDL) cholesterol levels were compared with those of an age-matched reference series of nonpregnant women, derived from the same cohort. Pregnant women showed higher total cholesterol levels (235 +/- 7.4 mg/100 ml) than nonpregnant women (205 +/- 2.7 mg/100 ml). Pregnant women also had higher levels of HDL cholesterol (66 +/- 2.1 mg/100 ml) than their referents (57 +/- 1.0 mg/100 ml). Total and HDL cholesterol increased with duration of pregnancy. When serum lipid levels of pregnant women were compared with the levels one year before and one year after pregnancy, it was observed that the year after pregnancy, HDL cholesterol levels dropped below pre-pregnancy concentrations. At the final examination, women who had ever been pregnant showed lower HDL cholesterol levels than those who had never been pregnant. The difference was most marked in users of oral contraceptives. These observations suggest that serum total and HDL cholesterol levels are elevated during pregnancy, probably because of hormonal changes. Furthermore, they point to a possibly lowering effect of parity on HDL cholesterol. These findings may help to explain the reported positive association between parity and the occurrence of cardiovascular diseases.