Childbearing, child-rearing, cardiovascular risk factors, and progression of carotid intima-media thickness: the Cardiovascular Risk in Young Finns study.

BACKGROUND AND PURPOSE Parity is associated with the risk of clinical cardiovascular events and the severity of preclinical atherosclerosis in older subjects. We sought to determine whether childbearing is associated with concurrent changes in cardiovascular risk factors and the progression of carotid intima-media thickness. METHODS We examined the association between the number of children born during a 6-year period and concurrent changes in cardiovascular risk factors and progression of carotid intima-media thickness in men and women of reproductive age from the Cardiovascular Risk in Young Finns study. Complete data for parity and carotid intima-media thickness were available for 1786 subjects (1005 females, 781 males). RESULTS For females, childbirth during the 6-year follow-up was associated with concurrent reductions in high-density lipoprotein cholesterol (P(trend)<0.0001), apolipoprotein A-I (P(trend)<0.0001), and apolipoprotein B (P(trend)=0.01); a redistribution of adiposity to abdominal deposits; and increased progression of carotid intima-media thickness (7.5+/-3.2 mum/birth [mean+/-SEM], P=0.02). The association of childbirth with carotid intima-media thickness progression was not greatly modified by adjustment for concurrent changes in cardiovascular risk factors (fully adjusted: P=0.05). This association was significantly stronger in females than males (P(heterogeneity)=0.001), who served as a control group exposed to the social and lifestyle influences of child-rearing but not the biological influences of childbearing. CONCLUSIONS The progression of carotid atherosclerosis over a 6-year period is increased in females who gave birth during the same period, independent of traditional risk factors. Mechanisms that underlie this observation possibly include parity-induced changes in nontraditional risk factors or an acute influence of pregnancy itself.