The rate of chronic hypertension during pregnancy has increased significantly in the United States since 1970 and is more common in older women and in black women, according to a population-based, cross-sectional analysis.
Researchers analyzed data from more than 151 million women with delivery-related hospitalizations in the United States between 1970 and 2010 and found that the rate of chronic hypertension in pregnancy increased steadily over time from 1970 to 1990, plateaued from 1990 to 2000, then increased again to 2010.
The analysis revealed an average annual increase of 6% – which was higher among white women than among black women – and an overall 13-fold increase from 1970 to 2010. These increases appeared to be independent of rates of obesity and smoking. The findings were published in.
The rates of chronic hypertension also increased with maternal age, among both black and white women.
“The strong association between age and rates of chronic hypertension underscores the potential for both biological and social determinants of health to influence risk,” wrote Cande V. Ananth, PhD, from the Rutgers University, New Brunswick, N.J., and coauthors. “The period effect in chronic hypertension in pregnancy is thus largely a product of the age effect and the increasing mean age at first birth in the U.S.”
The overall prevalence of chronic hypertension in pregnancy was 0.63%, but was twofold higher in black women, compared with white women (1.24% vs. 0.53%). The authors noted that black women experienced disproportionally higher rates of ischemic placental disease, pregestational and gestational diabetes, preterm delivery and perinatal mortality, which may be a consequences of higher rates of obesity, social disadvantage, smoking, and less access to care.
“This disparity may also be related to the higher tendency of black women to develop vascular disease at an earlier age than white women, which may also explain why the age-associated increase in chronic hypertension among black women is relatively smaller than white women,” they wrote. “The persistent race disparity in chronic hypertension is also a cause for continued concern and underscores the role of complex population dynamics that shape risks.”
This was the largest study to evaluate changes in the prevalence of chronic hypertension in pregnancy over time and particularly how the prevalence is influenced by age, period, and birth cohort.
In regard to the 13-fold increase from 1970 to 2010, the researchers suggested that changing diagnostic criteria for hypertension, as well as earlier access to prenatal care, may have played a part. For example, the American College of Cardiology recently modified their guidelines to include patients with systolic and diastolic blood pressures of 130-139 mm Hg and 80-89 mm Hg as stage 1 hypertension, which they noted would increase the prevalence rates of chronic hypertension during pregnancy.
The researchers reported having no outside funding and no conflicts of interest.
SOURCE: Ananth CV et al. Hypertension. 2019 Sept 9. .