Previous studies have reported declines in high density lipoprotein (HDL) cholesterol 1-2 years after pregnancy. In 1986-1996, the authors prospectively examined the association between childbearing and changes in fasting plasma lipids (low density lipoprotein, HDL, and total cholesterol; triglycerides) among 1,952 US women (980 Black, 972 White) in the Coronary Artery Risk Development in Young Adults study. Repeated-measures multiple linear regression was used to examine lipid changes over three time intervals (baseline to years 5, 7, and 10) in time-dependent follow-up groups: P0 (0 pregnancies), P1 (>/=1 miscarriages/abortions), B1 (1 birth), and B2 (>/=2 births). Means stratified by race and baseline parity (nulliparous or parous) were fully adjusted for study center, time, height, baseline diet, and other baseline and time-dependent covariates (age, smoking, education, weight, waist circumference, alcohol intake, oral contraceptive use, physical activity, short pregnancies). For both races, fully adjusted HDL cholesterol declines of -3 to -4 mg/dl were associated with a first birth versus no pregnancies during follow-up (p < 0.001). Higher-order births were not associated with greater declines in HDL cholesterol (B2 similar to B1, no association among women parous at baseline). In Whites, total and low density lipoprotein cholesterol declines were associated with follow-up births. HDL cholesterol declines of -3 to -4 mg/dl after a first birth persisted during the 10 years of follow-up independent of weight, central adiposity, and selected behavior changes.