Antenatal pyelonephritis hospitalisation trends, risk factors and associated adverse outcomes: A retrospective cohort study.

Objective: To analyse trends, risk factors and adverse outcomes associated with antenatal pyelonephritis hospitalisations.

Design: Retrospective cohort.

Setting: A national sample of US delivery hospitalisations with associated antenatal hospitalisations.

Population: US delivery hospitalisations in the Nationwide Readmissions Database from 2010 to 2020.

Methods: Antenatal hospitalisations with a pyelonephritis diagnosis within the 9 months before delivery hospitalisation were analysed. Clinical, demographic and hospital risk factors associated with antenatal pyelonephritis hospitalisations were analysed with unadjusted and adjusted logistic regression models with unadjusted and adjusted odds ratios as measures of effect. Temporal trends in antenatal pyelonephritis hospitalisations were analysed with Joinpoint regression to determine the relative measure of average annual percent change (AAPC). Risk for severe maternal morbidity and sepsis during antenatal pyelonephritis hospitalisations was similarly analysed with Joinpoint regression.

Results: Of an estimated 10.2 million delivery hospitalisations, 49 140 (0.48%) had an associated antenatal pyelonephritis hospitalisation. The proportion of deliveries with a preceding antenatal pyelonephritis hospitalisation decreased by 29% from 0.56% in 2010 to 0.40% in 2020 (AAPC -2.9%, 95% CI -4.0% to -1.9%). Antenatal pyelonephritis decreased, but risk for sepsis diagnoses increased during these hospitalisations from 3.7% in 2010 to 18.0% in 2020 (AAPC 17.2%, 95% CI 14.2%-21.1%). Similarly, risk for severe morbidity increased from 2.6% in 2010 to 4.4% in 2020 (AAPC 5.5%, 95% CI 0.8%-10.7%).

Conclusion: Antenatal pyelonephritis admissions appear to be decreasing in the USA. However, these hospitalisations are associated with a rising risk for sepsis and severe maternal morbidity.