Concerning Trends in Maternal Risk Factors in the United States: 1989-2018

Background: Increased efforts have focused on reducing maternal morbidity and mortality in the United States (US). Hypertensive disorders of pregnancy, chronic hypertension, diabetes mellitus, very advanced maternal age, and grand multiparity are known contributors to various maternal morbidities, as well as maternal mortality. We aimed to evaluate the trends in these risk factors/complications among US pregnancies during the last three decades (1989-2018).

Methods: This is a retrospective study based on the CDC natality database. We calculated the annual prevalence of each risk factor/complication from 1989 to 2018. Joinpoint regression analysis was then used to evaluate the trends. Annual percentage changes (APC) were calculated for each of the segments identified by the joinpoint regression, and average annual percentage changes (AAPC) were calculated for the entire period. Relative risks (RR) comparing the prevalence of each risk factor/complication in 2018 to its prevalence in 1989 were also calculated. Subsequent analyses evaluated the trends of the main risk factors/complications by maternal age groups. Statistical significance was determined at <0·05, and results were presented with 95% confidence intervals.

Findings: Between 1989 and 2018, the prevalence of hypertensive disorders of pregnancy increased by 149% (AAPC 3·2, 95% CI 2·6-3·8), that of chronic hypertension increased by 182% (AAPC 3·7, 95% CI 3·3-4·2), that of diabetes mellitus increased by 261% (AAPC 4·6, 95% CI 4·0-5·2), that of very advanced maternal age increased by 194% (AAPC 3·8, 95% CI 3·6-4·0), and that of grand multiparity increased by 33% (AAPC 1·0, 95% CI 0·8-1·2). Chronic hypertension and diabetes mellitus increased mostly during the past two decades, while hypertensive disorders of pregnancy and grand multiparity increased primarily over the most recent decade. Additionally, women of very advanced maternal age had significantly higher rates of hypertensive disorders of pregnancy, chronic hypertension and diabetes mellitus throughout our study period.

Interpretation: Our study shows a marked increase in the prevalence of five pregnancy risk factors/complications over the past three decades (1989-2018). This may point to a significant deterioration in the health of US pregnant women, which potentially contributes to both maternal morbidity and mortality.

Funding: None.