Assessing Risk Factors for Infant Mortality in the US: State of the Art

Objective: To examine multiple infant and maternal risk factors for infant mortality.

Study Design: This cross-sectional study used data from 2017-2018 National Center for Health Statistics (NCHS) Cohort Linked Live Birth-Infant Death Files, consisting of all births occurring in 2017 and all infant deaths occurring in 2018 linked to their corresponding birth certificates.

Results: The 2017-2018 birth cohort linked birth/infant death data included 3,723,134 singletons in total. The number of infant deaths was 19,026, yielding an infant mortality rate (IMR) of 5.1 per 1,000 live births. We identified four most severe risk factors for infant mortality, including extremely low birth weight (< 1000 g), presence of congenital anomalies (CAs), 5-minute Apgar score <7, and extremely preterm (gestational age <28 weeks), with the associated IMRs ranging from 120-370 and associated adjusted odds ratios (AORs) ranging from 3-25. Their IMRs and AORs were, respectively, extremely low birth weight (IMR: 370.8; AOR: 24.85), presence of CAs (IMR: 119.5; AOR: 17.52), 5-minute Apgar score <7 (IMR: 140.8; AOR: 11.89), and extremely preterm (IMR: 343.6; AOR: 3.13). Other significant risk factors were infant male gender and several maternal factors, including age less than 20 years, AIAN race, high school education or less, unmarried status, inadequate or excessive GWG, smoking before or during pregnancy, lack of prenatal care, hypertension or diabetes before or during pregnancy, previous death of a live birth, and payment source for delivery as Medicaid, Self-Pay or Other, with AORs ranging from 1.1 to 2.

Conclusions: This study identified multiple infant and maternal risk factors for infant mortality. Identification of these risk factors could aid in infant mortality reduction by improving prenatal care, maternal and child health programs and policies through the joint collaborations between health care providers, states, communities, and partners.

Keywords: Infant mortality rate; risk factors; multivariate logistic regression; adjusted odds ratio.