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Original Investigation
October 13, 2021

Preterm Delivery and Long-term Risk of Hypertension in Women

Author Affiliations
  • 1Department of Family Medicine and Community Health, Icahn School of Medicine at Mount Sinai, New York, New York
  • 2Department of Population Health Science and Policy, Icahn School of Medicine at Mount Sinai, New York, New York
  • 3Center for Primary Health Care Research, Lund University, Malmö, Sweden
JAMA Cardiol. Published online October 13, 2021. doi:10.1001/jamacardio.2021.4127
Key Points

Question  What are the long-term risks of hypertension in women who deliver preterm?

Findings  In this cohort study of more than 2 million women in Sweden, after adjusting for preeclampsia, other hypertensive disorders of pregnancy, and other maternal factors, women who delivered preterm had a greater than 1.6-fold risk of hypertension and women who delivered extremely preterm had a 2.2-fold risk within the next 10 years compared with those who delivered full term. These risks decreased but remained significantly elevated 40 years later and were not explained by shared familial factors.

Meaning  These results suggest that preterm delivery is a lifelong risk factor for hypertension in women.

Abstract

Importance  Preterm delivery has been associated with future cardiometabolic disorders in women. However, the long-term risks of chronic hypertension associated with preterm delivery and whether such risks are attributable to familial confounding are unclear. Such knowledge is needed to improve long-term risk assessment, clinical monitoring, and cardiovascular prevention strategies in women.

Objective  To examine the long-term risks of chronic hypertension associated with preterm delivery in a large population-based cohort of women.

Design, Setting, and Participants  This national cohort study assessed all 2 195 989 women in Sweden with a singleton delivery from January 1, 1973, to December 31, 2015. Data analyses were conducted from March 8, 2021, to August 20, 2021.

Exposures  Pregnancy duration identified from nationwide birth records.

Main Outcomes and Measures  New-onset chronic hypertension identified from primary care, specialty outpatient, and inpatient diagnoses using administrative data. Cox proportional hazards regression was used to compute hazard ratios (HRs) while adjusting for preeclampsia, other hypertensive disorders of pregnancy, and other maternal factors. Cosibling analyses were assessed for potential confounding by shared familial (genetic and/or environmental) factors.

Results  In 46.1 million person-years of follow-up, 351 189 of 2 195 989 women (16.0%) were diagnosed with hypertension (mean [SD] age, 55.4 [9.9] years). Within 10 years after delivery, the adjusted HR for hypertension associated with preterm delivery (gestational age <37 weeks) was 1.67 (95% CI, 1.61-1.74) and when further stratified was 2.23 (95% CI, 1.98-2.52) for extremely preterm (22-27 weeks of gestation), 1.85 (95% CI, 1.74-1.97) for moderately preterm (28-33 weeks of gestation), 1.55 (95% CI, 1.48-1.63) for late preterm (34-36 weeks of gestation), and 1.26 (95% CI, 1.22-1.30) for early-term (37-38 weeks of gestation) compared with full-term (39-41 weeks of gestation) delivery. These risks decreased but remained significantly elevated at 10 to 19 years (preterm vs full-term delivery: adjusted HR, 1.40; 95% CI, 1.36-1.44), 20 to 29 years (preterm vs full-term delivery: adjusted HR, 1.20; 95% CI, 1.18-1.23), and 30 to 43 years (preterm vs full-term delivery: adjusted HR, 95% CI, 1.12; 1.10-1.14) after delivery. These findings were not explained by shared determinants of preterm delivery and hypertension within families.

Conclusions and Relevance  In this large national cohort study, preterm delivery was associated with significantly higher future risks of chronic hypertension. These associations remained elevated at least 40 years later and were largely independent of other maternal and shared familial factors. Preterm delivery should be recognized as a lifelong risk factor for hypertension in women.

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