Parity and risk of later-life maternal cardiovascular disease
Received 18 September 2009; accepted 18 November 2009.
Background
Prior studies relating parity with maternal cardiovascular disease (CVD) have been performed in relatively small study samples without accounting for pregnancy-related complications associated with CVD.
Methods
We examined the associations between parity and maternal risk of later-life CVD in a population-based cohort study using data from the Swedish population registers. Women born from 1932 to 1955 were followed until the occurrence of CVD, death, emigration, or end of follow-up (December 31, 2005). Cox proportional hazards models were used to estimate associations between parity and risk of CVD accounting for birth year, yearly income, education level, country of birth, hypertension (pregestational hypertension or gestational hypertension, with or without proteinuria), diabetes (type 1, type 2, or gestational diabetes), preterm birth, small for gestational age, and stillbirth.
Results
During a median follow-up time of 9.5 years (range 0-23.5), there were 65,204 CVD events in the full sample of women. Among 1,332,062 women, parity was associated with CVD in a J-shaped fashion, with 2 births representing the nadir of risk (global P value < .0001). Upon accounting for pregnancy-related complications in a subset of women with at least 1 childbirth after 1973 (n = 590,725), the association of parity with CVD was similar. Compared with women with 2 childbirths, the multivariable-adjusted hazard ratios (95% CIs) for women with 1 and ≥5 births were 1.09 (1.03-1.15) and 1.47 (1.37-1.57), respectively.
Conclusions
In conclusion, parity was associated with incident maternal CVD in a J-shaped fashion, even after accounting for socioeconomic factors and pregnancy-related complications.
aCardiovascular Division and Cardiovascular Epidemiology and Research Unit, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA
bClinical Epidemiology Unit, Department of Medicine, Karolinska University Hospital, Karolinska Institutet, Sweden
cDepartment of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden
dDepartment of Pediatrics, Örebro University Hospital, Örebro, Sweden
Reprint requests: Erik Ingelsson, MD, PhD, Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Box 281, SE-171 77 Stockholm, Sweden.
ABSTRACT