One-year mortality disparities between infants of unmarried and married families in South Korea: a large scale retrospective cohort study.

Background: This study examined disparities in 1-year mortality rates between infants born to married and unmarried single-parent families, emphasizing the need for targeted health policies.

Methods: Data from 3,298,263 cases, obtained from the South Korea National Statistical Office (2010-2017), were analyzed. T-tests and chi-square tests were used to assess the demographic characteristics of the study group. The number of deaths per 1,000 live births was calculated, and logistic and multivariable logistic regressions were employed to compare infant mortality rates between family types. Additional stratified analyses, based on gestational age and birth weight, further elucidated the relationship between parental marital status and infant mortality.

Results: Infants from unmarried families exhibited a 3.34-fold higher crude odds ratio (OR) for 1-year mortality (95% confidence interval [CI], 2.56-4.36; P<0.001) than that from married families. After adjusting for confounders, the adjusted OR was 1.40 (95% CI, 1.03-1.92). Stratification by gestational age and birth weight revealed crude ORs of 4.62 (95% CI, 3.34- 6.39) in non-preterm infants (≥37 weeks) and 4.76 (95% CI, 3.46-6.56) in non-low-birth-weight infants (≥2.5 kg), highlighting a more pronounced disparity in infants born at or above normal weight and full term. No significant difference (P>0.05) was found in the crude OR for 1-year mortality rates among low-birth-weight (<2.5 kg) or preterm (<37 weeks) infants between the two-family types. Conclusion: This study highlights the significant disparity in infant mortality rates based on parental marital status, underscoring the need for enhanced social support and tailored policies for unmarried single-parent families.