The Department of Defense Birth and Infant Health Research Program: Characteristics of Live Births and Adverse Birth and Infant Health Outcomes Among TRICARE Beneficiaries, 2016-2021.

Introduction: The Department of Defense Birth and Infant Health Research (BIHR) program regularly identifies live births among TRICARE beneficiaries (i.e., United States military-connected families) for epidemiologic surveillance and research purposes. Linkage of infants with their TRICARE sponsor and birth mother (who may also be the sponsor) provides the capability to examine parental and military characteristics of births and associated health outcomes. The current study describes BIHR data methodology and presents population characteristics for a recent, 6-year cohort of live births among military families.

Materials and methods: The study cohort comprised all infants in BIHR data born January 2016 through December 2021. Same-sex multiples were not captured because of difficulty differentiating their neonatal medical records. Infants were identified and linked with sponsors and birth mothers using data from the Military Health System Data Repository and Defense Manpower Data Center, which were also used to derive demographic, military, and medical characteristics. Birth and infant health outcomes were ascertained using diagnosis and procedure codes from medical encounter files, which encompassed all care covered by TRICARE (i.e., across military and civilian facilities). Population characteristics were reported using descriptive statistics, overall and by birth mother beneficiary type: sponsor, dependent spouse, or other. Trends in selected adverse outcomes were also described (i.e., cesarean delivery, preterm birth [<37 weeks' gestation], low birthweight [<2500 g], and birth defects).

Results: There were 632,565 live births identified from 2016 to 2021; birth mother beneficiary type was most frequently dependent spouse (78.0%, n = 493,183), followed by sponsor (17.3%, n = 109,293) and other (4.8%, n = 30,089). Overall, mean maternal age at delivery was 28.4 years; the majority of infants had sponsors who were married (89.3%, n = 564,999), non-Hispanic White (60.7%, n = 384,148), on active duty status (73.1%, n = 462,107), and of any enlisted rank (79.6%, n = 503,848). Most infants' sponsors deployed at least once before their birth (57.0%, n = 360,312), with a smaller proportion deployed during pregnancy (7.5%, n = 47,306). Births were more likely to occur at civilian versus military hospitals, and the proportion of births at civilian hospitals increased over the study period, from 61.6% in 2016 to 69.5% in 2021. Among all infants, 28.2% (n = 178,589) were delivered by cesarean, 7.3% (n = 45,940) were preterm, 5.2% (n = 32,605) were low birthweight, and 3.4% (n = 21,222) were diagnosed with a major structural birth defect in the first year of life; all of these outcomes were more likely to occur among civilian versus military hospital births.

Conclusions: Overall, BIHR data comprise a large number of live births with distinct parental demographic and exposure characteristics. Data can be leveraged to examine adverse health outcomes and various aspects of health care delivery among infants born to United States military-connected families.