Association between interpregnancy interval and future risk of maternal cardiovascular disease—a population‐based record linkage study

OBJECTIVE: To examine the associations between interpregnancy interval and later maternal cardiovascular disease (CVD) risk. DESIGN: Population-based record linkage study. SETTING: New South Wales, Australia, 1994-2011. POPULATION: 216 467 women having first and second liveborn singleton infants, excluding those with an existing or pregnancy-related CVD risk factor. METHODS: We linked birth records of mothers to the mothers' subsequent CVD (coronary heart disease, cerebrovascular events, and chronic heart failure) hospitalisation or death. Multivariable Cox proportional hazard regression was used to estimate adjusted hazard ratios (AHR) 95% confidence interval (CI), accounting for maternal age, parity, socioeconomic status, and smoking during pregnancy. MAIN OUTCOME MEASURES: The first occurrence of a CVD hospitalisation or death after the second birth. RESULTS: In comparison with mothers with an interpregnancy interval of 18-23 months (reference category), the AHR among mothers with interpregnancy interval of <12 months was 1.56 (95% CI 1.18-2.07) and of 12-17 months was 1.13 (95% CI 0.84-1.51). The AHRs were 1.40 (95% CI 1.07-1.82), 1.87 (95% CI 1.21-2.89), and 3.41 (95% CI 1.07-10.91), corresponding to interpregnancy intervals of 24-59, 60-119, and ≥120 months, respectively. AHRs of specific CVD categories showed a similar pattern. CONCLUSIONS: Interpregnancy interval is associated with the risk of subsequent maternal CVD in a J-shaped fashion. The association is independent of the existing and pregnancy-related CVD risk factors analysed. Both short and long interpregnancy intervals can be used as risk markers to identify women with an elevated CVD risk later in life. TWEETABLE ABSTRACT: Interpregnancy interval is associated with the risk of subsequent maternal cardiovascular disease in a J-shaped fashion.