Association between hypertensive disorders of pregnancy and placenta accreta spectrum

Placenta accreta spectrum and hypertensive disorders of pregnancy are two significant contributors to severe maternal morbidity and fetal prematurity that may have related but opposite uteroplacental vascular origins. However, the relationship between these conditions is uncertain. Our aim was to evaluate the association between placenta accreta spectrum and hypertensive disorders of pregnancy while accounting for differences in the amount of time at risk for developing clinical manifestations of hypertensive disorders of pregnancy.

A cross-sectional study using the National Inpatient Sample in the United States, 2017-2021. To reduce limitations of administrative coding for placenta accreta spectrum, the analysis was restricted to deliveries at <37 weeks' gestation. Incidence rates and unadjusted incidence rate ratios were calculated, using gestational weeks to account for the person-time-at-risk of developing hypertensive disorders of pregnancy. Multivariable Poisson regression models were used to examine the association between placenta accreta spectrum and hypertensive disorders of pregnancy after adjusting for confounding factors.

Among 3,583,780 delivery hospitalizations between 2017 and 2021, 1,798,540 (unweighted n = 359,708) deliveries between ≥20 and <37 weeks were included. A total of 0.7% of individuals had placenta accreta spectrum, and 29.8% had hypertensive disorders of pregnancy. The incidence of hypertensive disorders of pregnancy significantly differed between those with and without placenta accreta spectrum (11.5 vs. 20.6 cases per 1000 person-gestational weeks) with an unadjusted incidence rate ratio of 0.56 (95% confidence interval [CI] 0.51-0.61). After controlling for confounding factors, hypertensive disorders of pregnancy remained significantly lower in individuals with placenta accreta spectrum (adjusted incidence rate ratio 0.80, 95% CI 0.73-0.87).

Using a large, nationally representative dataset, hypertensive disorders of pregnancy had a significant inverse association with placenta accreta spectrum disorders.