Incidence Trends and Risk Factor Variation in Severe Intraventricular Hemorrhage across a Population Based Cohort.

Objective: To quantify the current burden of severe intraventricular hemorrhage (IVH), describe time trends in severe IVH, identify IVH-associated risk factors, and determine the contribution of mediating factors.

Study Design: The retrospective cohort included infants 22-31 weeks of gestation without severe congenital anomalies, born at hospitals in the California Perinatal Quality Care Collaborative between 2005 and 2015. The primary study outcome was severe (grade III or IV) IVH.

Results: Of 44 028 infants, 3371 (7.7%) had severe IVH. The incidence of severe IVH decreased significantly across California from 9.7% in 2005 to 5.9% in 2015. After stratification by gestational age, antenatal steroid exposure was the only factor associated with a decreased odds of severe IVH for all gestational age subgroups. Other factors, including delivery room intubation, were associated with an increased odds of severe IVH, though significance varied by gestational age. Factors analyzed in the mediation analysis accounted for 45.6% (95% CI 38.7%-71.8%) of the reduction in severe IVH, with increased antenatal steroid administration and decreased delivery room intubation mediating a significant proportion of this decrease, 19.4% (95% CI 13.9%-27.5%) and 27.3% (95% CI 20.3%-39.2%), respectively. The unaccounted proportion varied by gestational age.

Conclusions: The incidence of severe IVH decreased across California, associated with changes in antenatal steroid exposure and delivery room intubation. Maternal, patient, and delivery room factors accounted for less than one-half of the decrease in severe IVH. Study of other factors, specifically neonatal intensive care unit and hospital-level factors, may provide new insights into policies to reduce severe IVH.