Preterm Deliveries Linked to Increased Risk of Ischemic Heart Disease


A new analysis of more than 47 million person-years of data indicates women who delivered a baby preterm were at a greater risk of developing ischemic heart disease.

Casey Crump, MD, PhD

Casey Crump, MD, PhD

New research from an analysis of the Swedish Medical Birth Registry suggests women experience preterm delivery were at an increased risk of developing ischemic heart disease (IHD) later in life.

With almost 10% of births in the US occurring before 37 weeks, results of the study, which included more than 47 million person-years of follow-up data, highlight the need for routine cardiovascular risk assessments in women.

"Cardiovascular risk assessment in women should routinely include reproductive history that covers preterm delivery and other pregnancy complications. Women with a history of preterm delivery may warrant early preventive actions to reduce other IHD risk factors, including obesity, physical inactivity, and smoking, and long-term monitoring for timely detection and treatment of IHD," said lead investigator Casey Crump, MD, PhD, professor of family medicine and community health at the Icahn School of Medicine at Mount Sinai in New York, in a statement.

With women who deliver preterm at an increased risk of multiple cardiovascular complications, Crump and a team of colleagues sought to develop a greater understanding of long-term risks associated with preterm delivery and possible interventions to prevent these risks. To do so, investigators designed an analysis using data from the Swedish Medical Birth Registry.

Using a time period lasting from 1973-2015, investigators identified 2,189,190 women who had a singleton delivery in Sweden. With data from the Swedish Hospital, Outpatient, and Death Registries, investigators were able to obtain 9information related to deaths, causes of death, diagnoses of IHD, and multiple covariates including maternal age, BMI, smoking status, and histories of conditions such as hypertension.

Over 47.5 million person-years of follow-up, 2.3% (n=49,955) of women developed IHD. Upon analysis, median age at delivery for the cohort was 27.3 years, median age at IHD diagnosis was 57.4 years, and median age at the end of follow-up was 50.5 years.

Upon analysis, the prevalence of hypertension at the end of follow-up was 20.3% among women who delivered pre-term. Further analysis indicated the prevalence among women was 20% among women who delivered between 22-27 weeks, 22.4% for those who delivered from 28-33 weeks, 19.6% for the whole delivered between 34-36 weeks, and 17.5% for those who delivered early-term. In comparison, prevalence among those with only full-term deliveries was only 16.6%. 

In adjusted analyses, adjusted hazard ratio for developing IHD among women who gave birth pre-term was 2.47 (95% CI, 2.16-2.82) compared to those who had full-term births. Additional analysis indicated this figure was 4.04 (95% CI, 2.69-6.08) for those who delivered between 22-27 weeks, 2.62 (95% CI, 2.09-3.29) for those who delivered between 28-33 weeks, 2.30 (95% CI, 1.97-2.70) for those who delivered between 34 to 36 weeks, and 1.47 (95% CI, 1.30-1.65) for those who delivered between 37-38 weeks. Investigators also pointed out the risk appeared to decline but remained significantly elevated after additional follow-up.

Investigators noted multiple limitations within their study. Limitations included the possibility of incompletely controlled confounders, being unable to verify IHD diagnosis due to availability of detailed clinical data, and possible underreporting of IHD.

"The higher IHD risk in women who had preterm birth persisted in co-sibling analysis, suggesting that shared genetic or environmental factors did not underlie the association with IHD. The novel results are a call to action for further development of the field of cardio-obstetrics,” said Anne Marie Valente, MD, Director of the Boston Adult Congenital Heart Program at Boston Children's Hospital/Brigham and Women's Hospital, in an accompanying editorial comment.

This study, “Pre-Term Delivery and Risk of Ischemic Heart Disease in Women,” was published in the Journal of the American College of Cardiology.

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