The cohort study of more than 2 million women in Sweden took into account preeclampsia, other hypertensive disorders of pregnancy and other maternal factors.
The risk of hypertension decreased but remained significantly elevated 40 years postpartum, but was largely independent of other shared maternal and family factors.
“These results suggest that preterm birth is a lifelong risk factor for hypertension in women,” the authors wrote.1
The national cohort study assessed the 2,195,989 women in Sweden who gave birth to a single child between January 1973 and December 2015.
New-onset chronic hypertension was identified from primary care, specialist outpatient and inpatient diagnoses via administrative data.
Over 46.1 million person-years of follow-up, 16.0% of women were diagnosed with hypertension at a mean age of 55.4 years.
In the 10 years following delivery, the adjusted hazard ratio (aHR) for hypertension related to preterm delivery (gestational age
Compared to term delivery (39 to 41 weeks gestation), the aHR was 2.23 for very preterm infants (22 to 27 weeks gestation); 1.85 for moderately preterm (28 to 33 weeks gestation); 1.55 for late preterm infants (34 to 36 weeks of gestation); and 1.26 for early term (37 to 38 weeks gestation).
These risks decreased but remained significantly high between 10 and 19 years after delivery: aHR of 1.40 for preterm delivery compared to term delivery.
Further, the aHR was 1.20 for 20-29 years and 1.12 for 30-43 years postpartum when comparing preterm versus term delivery.
“These findings were not explained by shared determinants of preterm birth and hypertension within families,” the authors wrote.
Women with recurrent preterm births were at even higher risk. For example, for each additional preterm birth within 10 years of follow-up, the aHR was 1.51; which decreased to 1.28 at 10 to 19 years of follow-up, 1.12 at 20 to 29 years of follow-up, and 1.10 at 30 to 43 years of follow-up (P
Spontaneous and medically indicated preterm or early term deliveries were associated with increased risks of chronic hypertension compared to term delivery: aHR of 1.25 (PP
Medically indicated preterm delivery that was specifically related to preeclampsia or other hypertensive disorders of pregnancy had an aHR of 1.67; 95% CI: 1.62 to 1.73 (P
Similarly, chronic hypertension due to preterm delivery for other indications, primarily diabetes, had an aHR of 1.41; 95% CI: 1.35 to 1.47; (P
The study findings are consistent with previously reported links between preterm birth and long-term risks of stroke, ischemic heart disease, and all-cause mortality and cardiovascular disease, according to the authors.
“Preterm birth should now be recognized as a lifelong risk factor for hypertension,” they wrote.
The authors also noted that women with a history of preterm birth need early preventive assessment and long-term risk reduction and monitoring for hypertension.
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Reference
- Crump C, Sundquist J, Sundquist K. Preterm birth and long-term risk of hypertension in women. JAMA-cardiol. Published online October 13, 2021. doi:10.1001/jamacardio.2021.4127
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