Preterm delivery tied to risk for future chronic hypertension
Among more than 2 million women in Sweden, preterm delivery yielded a significantly increased risk for future chronic hypertension, an association that persisted at least 40 years later, according to data published in JAMA Cardiology.
“Preterm delivery should now be recognized by clinicians and patients as an important risk factor for hypertension across the life course,” Casey Crump, MD, PhD, vice chair for research in the department of family medicine and community health and professor of epidemiology in the department of population health science and policy at Icahn School of Medicine at Mount Sinai, told Healio.
In discussing the catalyst for the study, Crump cited the 2017 American College of Cardiology/American Heart Association hypertension guideline stating the condition affects nearly one in two women worldwide.
“Certain pregnancy complications, especially preeclampsia and other hypertensive disorders of pregnancy, are associated with preterm delivery and also with subsequent development of chronic hypertension,” he said. “However, the independent contribution of preterm delivery to long-term risks of hypertension is unclear. A better understanding of these risks is needed to improve risk stratification, clinical monitoring and CVD prevention in women.”
Crump and colleagues conducted a national cohort study assessing 2,195,989 women in Sweden with a singleton delivery from 1973 to 2015.
New-onset chronic hypertension identified from primary care, specialty outpatient and inpatient diagnoses using administrative data served as the main outcome measure. Preterm delivery was defined as a gestational age less than 37 weeks, whereas extremely preterm was 22 to 27 weeks, moderately preterm was 28 to 33 weeks, late preterm was 34 to 36 weeks, early term was 37 to 38 weeks and full term was 39 to 41 weeks.
During 46.1 million person-years of follow-up, 16% of women (mean age, 55 years) were diagnosed with hypertension.
Compared with full-term delivery, preterm delivery was associated with increased risk for hypertension within 10 years of delivery (adjusted HR = 1.67; 95% CI, 1.61-1.74). After further analysis, the adjusted HR was 2.23 (95% CI, 1.98-2.52) for extremely preterm, 1.85 (95% CI, 1.74-1.97) for moderately preterm, 1.55 (95% CI, 1.48-1.63) for late preterm and 1.26 (95% CI, 1.22-1.3) for early-term compared with full-term delivery.
In longer follow-up, the hypertension risk for preterm compared with full-term delivery lowered, but remained significantly heightened at 10 to 19 years (aHR = 1.4; 95% CI, 1.36-1.44), 20 to 29 years (aHR = 1.2; 95% CI, 1.18-1.23) and 30 to 43 years (aHR = 95% CI, 1.12; 95% CI, 1.1-1.14) after delivery.
The researchers reported that these findings were not explained by shared determinants of preterm delivery and hypertension within families. Crump said other studies have suggested that preterm delivery may trigger endothelial-specific inflammation that leads to functional changes in the microvasculature, including increased constrictive tone and higher BP.
“Cardiovascular risk assessment in women should routinely include reproductive history that covers preterm delivery,” Crump told Healio. “Women with a history of preterm delivery need early preventive actions to reduce other modifiable risk factors, including obesity, unhealthy diet, physical inactivity, excessive alcohol and smoking. These interventions should be implemented soon after preterm delivery, followed by long-term close monitoring for hypertension.”