Parity and Cardiovascular Disease Risk among Older Women: How Do Pregnancy Complications Mediate the Association?

Parity evaluated cross sectionally has been associated with increased risk of cardiovascular disease in women in many but not all studies. Some studies indicate that each live birth confers additional, albeit modest, risk for prevalent maternal cardiovascular disease1 or athlerosclerosis.2 Alternatively, other studies have found a threshold effect such that women with more than five or six children have excess cardiovascular disease risk.3 4 Risks associated with nulliparity are contradictory. Some studies indicate that nulliparous women are at lower risk compared to parous women; 2–5 others have found nulliparous women to be at higher risk for cardiovascular disease compared to parous women with one or two births.1, 6, 7 Separate studies have also found that certain pregnancy complications, including preeclampsia,8–11 preterm delivery,12, 13 and low birth weight14, 15 have been associated with excess maternal cardiovascular risk. Only one study to date has attempted to disaggregate the effects of parity and pregnancy complications on women’s long term cardiovascular risk. Hannaford found that nulliparaous women at an average age of 56 had an increased risk for developing hypertension or stroke compared to parous women whose births had been without complications from hypertension.6 We set out to assess the effect of parity on CVD prevalence, and determine if this effect was mediated by pregnancy complications. In particular, we sought to determine if parity was associated with higher prevalence of cardiovascular disease among older women after excluding those who had experienced at least one pregnancy complicated by preeclampsia, low birth weight, or preterm delivery. A secondary aim was to investigate how cardiovascular risk factors, including body composition, vascular, metabolic or inflammatory markers were related to parity, pregnancy complications, and maternal cardiovascular disease risk.