Perinatal mortality trend associated with maternal obesity in United States between 2015 - 2020.

Background: Obesity is associated with an increased risk of stillbirth and neonatal death. Since the publication of A Randomized Trial of Induction Versus Expectant Management (ARRIVE) in 2018, there was an increase in 39 weeks deliveries. The objective of this study was to evaluate the trends in perinatal mortality by BMI category from 2015 to 2020.

Study Design: This was a retrospective cohort study of US births between 2015 and 2020. The rates of stillbirths, infant deaths, and perinatal mortality were calculated for each BMI category. Logistic regression models were constructed based on specific outcome rates from 2015 - 2018 to predict the rates in 2019 and 2020. The predicted rates were compared with the actual rates to determine possible deviations due to policy and practice changes that occurred.

Results: Between 2015 - 2018, the stillbirth rate increased for ascending BMI categories. Whereas the neonatal death rate decreased for all except the underweight group, the perinatal death rate increased in all except for those with category III obesity. In 2019 the perinatal mortality rate decreased for every BMI category except underweight group. In 2020, the rate of infant deaths increased for all BMI categories compared with the predicted rates. The results were similar after excluding common comorbidities.

Conclusions: Perinatal mortality rates improved in 2019, reversing the increasing trend from 2015-2018. However this trend did not persist for some BMI categories in 2020. These findings may suggest a beneficial effect of policy changes since the ARRIVE trial publication and the negative effects from the COVID-19 pandemic.