Pre-term delivery was an independent predictor of future ischemic heart disease (IHD), according to a study published in the Journal of The American College of Cardiology.
In this national cohort study, women (n=2,189,190) who had singleton deliveries in Sweden between 1973 and 2015 without prior history of IHD and were in the Swedish Medical Birth Registry, were included. All participants were followed through the end of 2015 to determine the occurrence of IHD. Pregnancy duration was defined as extremely pre-term (22-27 weeks), very pre-term (28-33 weeks), late pre-term (34-36 weeks), early-term (37-38 weeks), full-term (39-41 weeks, used as reference), and post-term (≥42 weeks).
By study end, a total of 49,955 women (2.3%) were diagnosed with IHD. Among the women who delivered before 37 weeks of pregnancy, the 10-year adjusted hazard ratio (aHR) for developing IHD was 2.47 (95% CI, 2.16-2.82).
Within 10 years of giving birth, women who delivered extremely pre-term had the highest risk for IHD (aHR, 4.04; 95% CI, 2.69-6.08), followed by very pre-term (aHR, 2.62; 95% CI, 2.09-3.29), late pre-term (aHR, 2.30; 95% CI, 1.97-2.70), and early-term (aHR, 1.47; 95% CI, 1.30-1.65), compared with full-term births.
The risk of developing IHD was stable decades after giving birth. Between 10 and 19 years after having a child, the risk for IHD among women who delivered before 37 weeks of pregnancy was elevated (aHR, 1.86; 95% CI, 1.73-1.99), slowly decreasing with time since birth (20-29 years: aHR, 1.52; 95% CI, 1.45-1.59; 30-43 years: aHR, 1.38; 95% CI, 1.32-1.45).
To account for any cofactors which may have contributed to the underlying risk for IHD, a cosibiling analysis was performed. The aHRs for IHD when controlling for common genetics or environmental factors were: 2.84 (95% CI, 1.20-6.73) within 10 years of giving birth, 1.86 (95% CI, 1.73-1.99) between 10 and 19 years, 1.52 (95% CI, 1.45-1.59) between 20 and 29 years, and 1.38 (95% CI, 1.32- to 1.45) between 30 and 43 years. These comparable hazard ratios indicated that the risk for IHD was primarily due to some factors other than genetic predisposition or familial environment.
A major limitation of this study was the availability of IHD diagnosis data after 2001 only, which may have led to an underestimation of IHD occurrence.
“The findings suggest that preterm and early-term delivery are important independent risk factors for the development of IHD, and that the associated risks may persist up to 40 years
Later,” concluded the study authors. “Women who deliver prematurely need early preventive evaluation and long-term monitoring for IHD.”
Crump C, Sundquist J, Howell E A, et al. Pre-term delivery and risk of ischemic heart disease in women. J Am Coll Cardiol. 2020;76:57–67. doi:10.1016/j.jacc.2020.04.072