Mortality Among Twins Born to Unmarried Teenagers in the United States

Objective: The objective of this study is to determine the association between unmarried status and infant mortality among twins born to teenagers. Methods: We conducted a retrospective cohort study on twin live births to teenagers in the United States from 1995 through 1998 using the Vital Records assembled by the National Center for Health Statistics. We compared mortality estimates among twins of single to those of married mothers using the generalized estimating equation framework, which also adjusted for intracluster correlations. Results: Analysis involved 28592 individual twins of teenager mothers, with both cluster members being live-born. Out of these, 21.8% (n = 6238) were born to married and 78.2% (n = 22,354) to single mothers. Infant and postneonatal mortality was 17% and 36% higher among twins of single teenager mothers (odds ratio (OR) = 1.17; 95% confidence interval (CI) = 1.01–1.40) and (OR = 1.36; 95% CI = 1.01–1.87), respectively. However, neonatal mortality was comparable (OR = 1.12; 95% CI = 0.92–1.34). Twins of single mothers were also more likely to be of low birth weight, very low birth weight, preterm and very preterm (p < 0.0001) but had the same risk level for smallness for gestational age as compared to twins of married teenagers. Conclusions: Single motherhood was associated with increased infant mortality among twins born to teenagers. The critical time of elevated risk was the postneonatal period and the survival disadvantage of twins of single mothers was as a result of the higher-than-expected level of preterm rather than small for gestational age births. These findings have potential clinical and public health relevance.