Maternal risk stratification and planned birth improve pregnancy outcomes at term: a population-based cohort study

In many countries, antenatal maternal risk stratification and individualization of subsequent pregnancy care are ubiquitous. However, because of the dynamic nature of pregnancy and emergence of new risk factors as gestation progresses, it is unclear whether this approach results in better pregnancy outcomes.

This study aimed to investigate the relationship between antenatal maternal risk stratification and maternal and perinatal outcomes, and to ascertain if planned birth at 39 weeks of gestation resulted in better pregnancy outcomes at term.

This was a retrospective cohort study of 1,167,372 singleton births at ≥37⁺⁰ weeks' gestation, conducted from 2000 to 2021 in Queensland, Australia. Women were stratified into 3 risk categories (high, intermediate, or low) in accordance with recommendations from international guidelines. The study outcomes were severe adverse maternal outcome, perinatal mortality (antepartum stillbirth, intrapartum stillbirth, and neonatal death), severe neonatal neurologic morbidity, and maternal-infant separation. Multivariable logistic regression models were built to determine odds ratios for the effect of maternal risk strata on study outcomes and the effect of planned birth (either induction of labor or scheduled cesarean delivery) at 39⁺⁰ to 39⁺⁶ weeks compared with expectant management.

A total of 468,710 (40.2%) women were categorized as low-risk, 324,650 (27.8%) as intermediate-risk, and 374,012 (32.0%) as high-risk. Compared with low-risk women, the odds of severe maternal adverse outcome, perinatal mortality, severe neonatal neurologic morbidity, and maternal-infant separation were increased in the intermediate- and high-risk groups, with the highest odds in the high-risk cohort. The probability of severe adverse maternal outcome was lowest at 39⁺⁰ to 39⁺⁶ weeks for all risk categories. Regardless of maternal risk stratum, the probability of perinatal mortality was lowest at 39⁺⁰ to 40⁺⁶ weeks, the probability of severe neonatal neurologic morbidity was lowest at 38⁺⁰ to 39⁺⁶ weeks, and the nadir for maternal-infant separation occurred at 39⁺⁰ to 40⁺⁶ weeks. For all study outcomes, the probability of an adverse outcome increased from 40⁺⁰ weeks onward regardless of risk category.

The risks of severe maternal and perinatal outcomes including maternal-infant separation are directly associated with antenatally determined maternal risk strata. Women in the high-risk category had the highest odds of all adverse outcomes. However, compared with expectant management, planned birth at 38⁺⁰ to 39⁺⁶ weeks, especially by scheduled cesarean delivery, was associated with the lowest odds of adverse outcomes, particularly for women in the high-risk category.