Contribution of Preterm Birth to Mortality Among Neonates with Birth Defects

To estimate the proportion of neonatal mortality risk attributable to preterm delivery among neonates with birth defects.

Using a statewide cohort of live born infants from the Texas Birth Defects Registry (1999-2014 deliveries), we estimated the population attributable fraction and 95% CI of neonatal mortality (death <28 days) attributable to prematurity (birth at <37 weeks vs ≥37 weeks) for 31 specific birth defects. To better understand the overall population burden, analyses were repeated for all birth defects combined.

Our analyses included 169 148 neonates with birth defects, of which 40 872 (24.2%) were delivered preterm. The estimated proportion of neonatal mortality attributable to prematurity varied by birth defect, ranging from 12.5% (95% CI: 8.7-16.1) for hypoplastic left heart syndrome to 71.9% (95% CI: 41.1-86.6) for anotia or microtia. Overall, the proportion was 51.7% (95% CI: 49.4-54.0) for all birth defects combined.

A large proportion of deaths among neonates with birth defects are attributable to preterm delivery. Our results highlight differences in this burden across common birth defects. Our findings may be helpful for prioritizing future work focused on better understanding the etiology of prematurity among neonates with birth defects and the mechanisms by which prematurity contributes to neonatal mortality in this population.