Trends in chronic hypertension in pregnancy

September 16, 2019
Judith M. Orvos, ELS

a BELS-certified medical writer and editor, and an editorial consultant for Contemporary OB/GYN

New research tracking the rate of chronic hypertension among pregnant women over 40 years has uncovered startling trends regarding its prevalence.

A new analysis of nationwide data shows that incidence of chronic hypertension during pregnancy in the United States increased sharply over a 40-year period. The trend, said researchers, was largely age-related but also revealed a striking race disparity.

Published in Hypertension, the findings are from a population-based cross-sectional analysis of more than 151 million women with delivery-related hospitalizations from 1970 to 2010. Possible risk factors for chronic hypertension examined by the authors were maternal age, year of delivery, maternal year of birth (birth cohort), and race.

The data from the study were taken from the National Hospital Discharge Survey (NHDS), which is compiled by the Centers for Disease Control and Prevention. NHDS reflects hospitalizations of less than 30 days in nonfederal and specialty facilities in 50 states and the District of Columbia.

The authors used age-period-cohort models to derive prevalence rates and rate ratios with 95% confidence intervals (CIs) of chronic hypertension in relation to age, period, and birth cohort. They also looked at whether the age-period-cohort effects were affected by changes in obesity and smoking rates.

During the four-decade period, the overall prevalence of chronic hypertension was 0.63% and the rate was more than twice as high in black women (1.24%) as in white women (0.53%; rate ratio, 2.31; 95% CI, 2.30-2.32). With advancing age and year of delivery, the rate of chronic hypertension increased sharply from 0.11% in 1970 to 1.52% in 2010 (rate ratio, 13.41; 95% CI, 13.22-13.61). The rate of hypertension increased, on average, by 5% per year and was slightly higher among white than among black women (7% and 4%, respectively).

The study, the authors said, is the largest to date in the United States of prevalence of chronic hypertension in pregnancy. They believe their findings are generalizable to pregnancies in this country because of the application of sampling weights in NHDS.

“The large temporal increase in the prevalence of chronic hypertension in pregnancy coupled with increasing rates with advancing maternal age, the researchers concluded, “suggests the need to further efforts to ensure better blood pressure control before and during pregnancy.” They recommended follow-up research on targeted prenatal interventions for chronic hypertension, race disparities in prevalence rates, and possible associations between chronic hypertension in pregnancy and increased risks of cardiovascular and cerebrovascular mortality and morbidity in women and their newborns later in life.