Risk and causes of early mortality among extremely preterm infants born small for gestational age.

Abstract

Objective: Extreme preterm (EPT) delivery, occurring before 28 weeks of gestation, carries high morbidity and mortality risks. Small for Gestational Age (SGA) infants, about 8-20% of EPT neonates, face increased risks. Mortality risk varies with gestational age and birth weight, with mixed reports on specific morbidities. This study aims to determine mortality rates and common causes of death among EPT SGA infants.

Study design: The study used data from the CDC National Vital Statistics System, covering births and deaths from 2016-2021, with follow-up through 2022. It included infants born between 22 and 27 weeks gestation who were admitted to the neonatal intensive care unit. The outcome was all-cause in-hospital mortality within 30 days of birth, with causes of mortality classified based on ICD-10 codes. Small for Gestational Age (SGA) was the primary independent variable.

Results: Based on a sample of N=96134 infants, we estimated 13% were born SGA and 30-day mortality rates were higher among SGA compared to non-SGA infants (31% vs. 13%). On multivariable analysis SGA infants had higher 30-day mortality than non-SGA (odds ratio: 3.82; 95% CI: 3.64, 4.01; p<0.001), and were more likely to have death ascribed to complications of short gestation rather than other causes of death (Relative Risk Ratio: 1.42; 95% CI: 1.27, 1.59; p<0.001).

Conclusions: SGA infants receiving intensive care have high mortality risk, especially due to complications of short gestation and low birthweight complications.