Parity and Cardiovascular Disease Risk among Older Women: How Do Pregnancy Complications Mediate the Association?
Introduction
Parity evaluated cross-sectionally has been associated with increased risk of cardiovascular disease (CVD) in women in many, but not all, studies. Some studies indicate that each live birth confers additional, albeit modest, risk for prevalent maternal CVD (1) or atherosclerosis (2). Alternatively, other studies have found a threshold effect such that women with more than five or six children have excess CVD risk 3, 4. Risks associated with nulliparity are contradictory. Some studies indicate that nulliparous women are at lower risk compared with parous women 2, 3, 4, 5; others have found nulliparous women to be at higher risk for CVD compared with parous women with one or two births 1, 6, 7.
Separate studies have also found that certain pregnancy complications, including preeclampsia 8, 9, 10, 11, preterm delivery 12, 13 and low birth weight 14, 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 et al. (6) found that nulliparous women at an average age of 56 had an increased risk for developing hypertension or stroke compared with parous women whose births had been without complications from hypertension.
We set out to assess the effect of parity on CVD prevalence and to determine whether this effect was mediated by pregnancy complications. In particular, we sought to determine whether parity was associated with higher prevalence of CVD 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 as well as vascular, metabolic or inflammatory markers were related to parity, pregnancy complications, and maternal CVD risk.
Section snippets
Participants
This was a cross-sectional study nested within the Health, Aging and Body Composition (Health ABC) Study. The Health ABC study is a large ongoing epidemiologic study of how changes in body composition affect morbidity, disability, and mortality. A total of 3,075 community dwelling participants (50% female) were enrolled in Pittsburgh, Pennsylvania and Memphis, Tennessee in the period 1997–1998. Recruitment procedures have been described elsewhere in detail (16). All participants signed an
Results
Of the 540 women studied, 89 (16.5%) reported no births, and 321 parous women (59.4%) reported no history of pregnancy complications of interest in this study. A total of 130 parous women (24.1%) reported at least one pregnancy complicated by preeclampsia or hypertension (n = 32), term low birth weight (n = 68), preterm birth (n= 64), or stillbirth (n = 9). There were 35 women who reported two or more affected births.
Parous women with no perinatal complications were younger and, as expected,
Discussion
Our results indicate that almost one fourth of the older women in our study reported a previous experience of at least one pregnancy complicated by the conditions of interest. Parous women with no pregnancy complications were twice as likely to have CVD compared with nulliparous women, and those with at least one complicated pregnancy had rates of CVD almost three times higher. High rates of statin use, lower HDL, and pregnancy complications accounted for some, but not all, of this excess CVD
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