323 - U.S. Infant Mortality by Gestational Age, 2015-2023

Publication Number: 4317.323

Elizabeth Wolf, Virginia Commonwealth University School of Medicine, Richmond, VA, United States; Miheret Yitayew, Children's Hospital of Richmond at VCU, Richmond, VA, United States; Nayef Chahin, Children's Hospital of Richmond at VCU, Richmond, VA, United States; Karen D.. Hendricks-Muñoz, Children's Hospital of Richmond at VCU, Richmond, VA, United States

Background: Resuscitation of extremely preterm infants has increased significantly since the 2015 Neonatal Resuscitation Program (NRP) lowered the viability threshold from 23 to 22 weeks. Care of the extremely preterm infant has improved with standardized prenatal, obstetric, and neonatal protocols, integrated multidisciplinary care teams, and greater attention to organ vulnerability. Despite these important advances, little is known about how infant mortality by gestational age has changed in recent years.

Objective: We aimed to use a comprehensive national database to understand how mortality has changed over time, stratified by each week of gestational age.

Design/Methods: We used all-cause infant mortality estimates from the US Centers for Disease Control and Prevention-Wide-Ranging Online Data for Epidemiologic Research (WONDER) linked birth-death database, which contains birth certificate and mortality data from all 50 states, Puerto Rico, and the District of Columbia. We used the most recent years (2015-2023) available. We obtained obstetrical estimates of gestational age 22-42 weeks. We excluded infants less than 22 weeks as these infants are rarely resuscitated and are typically classified as nonviable stillbirths.

Results: There were 33,795,010 births that met inclusion criteria of whom 15,807 (0.05%) were 22 weeks' gestation and 24,067 (0.07%) were 23 weeks' gestation. Mortality of 22-week and 23-week gestation infants declined significantly between the years 2015-2023 (Figure 1). Mortality for infants 22 weeks' gestation declined from 868 per 1000 live births (95% CI: 812-924) in 2015 to 732 per 1000 live births (95% CI: 679-786) in 2023. Mortality for infants 23 weeks' gestation declined from 593 per 1000 live births (95% CI: 557-628) in 2015 to 491 per 1000 live births (95% CI: 458-523) in 2023. Infant mortality at other gestational ages did not decrease significantly over the study period. For infants of 22- weeks' gestation, mortality was lower for those transferred to another hospital within 24 hours compared to non-transferred infants (data available 2017-2023).

Conclusion(s): All-cause mortality for infants of 22-23 weeks' gestation declined significantly in recent years while mortality remained stable for other gestational ages. Extreme preterm survivors often have major morbidities including dependence on medical technology. Increased survivorship of this population may present additional challenges to families and healthcare systems. Transfer to a level 3 or level 4 intensive care unit with advanced cardiopulmonary capabilities likely improves survival.

Figure 1
Infant Mortality per 1000 Live Births, by Gestational Age, 2017-2023

Table 1
Aggregate all-cause infant mortality by gestational age in weeks