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Pre-Term Delivery and Risk of Ischemic Heart Disease
Quick Takes
- Women with prior pre-term (<37 weeks) or early-term (37-38 weeks) delivery have increased risk for development of ischemic heart disease, up to 40 years after delivery.
- Identifying women with obstetric-related risk factors for heart disease is important for primary prevention.
- Further research into the mechanisms responsible for the association between pre-term deliveries and cardiovascular disease could help identify new targets for prevention.
Study Questions:
What are the long-term risks of ischemic heart disease (IHD) among women with a history of pre-term delivery?
Methods:
The Swedish Medical Birth Registry was used to identify 2,189,190 women with a singleton delivery (1973-2015). Women were followed up through 2015 for new-onset IHD. Adjusted hazard ratios (aHRs) for IHD associated with pregnancy duration were calculated using Cox regression. Cosibling analyses assessed the influence of shared genetic and/or environmental factors.
Results:
During follow-up, 49,955 (2.3%) women developed IHD. During the first 10 years after delivery, the aHR for IHD associated with pre-term delivery (<37 weeks) was 2.47 (95% confidence interval [CI], 2.16-2.82). Earlier deliveries were associated with increased risk: extremely pre-term (22-27 weeks) was 4.04 (95% CI, 2.69-6.08), for very pre-term (28-33 weeks) was 2.62 (95% CI, 2.09-3.29), for late pre-term (34-36 weeks) was 2.30 (95% CI, 1.97-2.70), and for early-term (37-38 weeks) was 1.47 (95% CI, 1.30-1.65), compared with full-term (39-41 weeks). The aHRs (pre-term vs. full-term) remained elevated for additional years of follow-up: 10-19 years: aHR, 1.86; 20-29 years: aHR, 1.52; 30-43 years: aHR, 1.38. More pre-term deliveries were associated with further increased risk, and findings did not appear related to familial genetic or environmental factors.
Conclusions:
Pre-term delivery was a strong independent risk factor for IHD. The associated risk remained elevated up to 40 years post-partum, but the association was strongest within the first 10 years after delivery.
Perspective:
This large national cohort study showed that women with prior pre-term delivery had a significantly increased long-term risk of IHD, even with adjustment for other maternal risk factors including pre-eclampsia, diabetes, obesity, and smoking. This study adds to the growing awareness of the importance of taking an obstetric history from our patients. Recently, the 2019 American College of Cardiology/American Heart Association Primary Prevention and 2018 Blood Cholesterol guidelines both stated that risk-enhancers such as adverse pregnancy outcomes (pre-eclampsia and hypertensive disorders of pregnancy, gestational diabetes, pre-term delivery, intrauterine growth restriction) should be considered when assessing cardiovascular risk in women. Although the addition of adverse pregnancy outcomes to standard risk calculators has not dramatically changed risk discrimination, there is clearly additive value for using the reproductive history, particularly in young women prior to the development of other classic risk factors. Early cardiovascular disease prevention and education for women with adverse pregnancy outcomes, such as pre-term delivery, could improve long-term outcomes.
Clinical Topics: Prevention, Smoking
Keywords: Diabetes Mellitus, Myocardial Ischemia, Obesity, Pre-Eclampsia, Pregnancy, Premature Birth, Primary Prevention, Risk Factors, Smoking, Women
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