Objective: Given growing interest in alternatives to hospital birth,
particularly given the COVID-19 pandemic, we developed a peripartum
intervention risk calculator (PIRC) to estimate maternal and neonatal
risk of requiring hospital-based peripartum intervention. Design:
National cohort study. Setting: United States. Sample: Hospital births
captured by the Pregnancy Risk Assessment Monitoring System from
2009-2018. Methods: The cohort was stratified by receipt of
hospital-based interventions, defined as: 1) operative vaginal delivery
(forceps or vacuum), 2) cesarean delivery, or 3) requiring neonatal
intensive care unit admission. Gravidas with prior cesarean delivery or
fetal malformation were excluded. Main Outcome Measures: Risk of
requiring hospital-based intervention. Results: A total of 63,234 births
were evaluated (72.6% full-term, 48.5% nulliparous) including 37.9%
who received one or more hospital–based interventions. Gestational age
was the most predictive factor of requiring hospital-based intervention,
with lowest odds at 400/7-406/7 weeks. Previous live births (Ref: none;
1, OR 0.41; 2, OR 0.35; ≥3, OR 0.29; p<0.05 for all) were
protective. Other predictors included advanced maternal age, high
pre-pregnancy body mass index, maternal diabetes, maternal hypertension,
and not exercising during pregnancy. The resulting seven-factor model
demonstrated strong discrimination (optimism corrected
C-statistic=0.776) and calibration (mean absolute error=0.009).
Conclusions: We developed and validated the PIRC for predicting
individualized risk for hospital-based intervention among gravidas based
on seven readily accessible prenatal factors. This calculator can
support personalized counseling regarding planned birth setting, helping
to close a critical gap in current clinical guidance and providing an
evidence-based risk assessment for those contemplating alternatives to
hospital birth.
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