Single motherhood and neonatal survival of twins among blacks and whites

OBJECTIVE: We investigated whether an association existed between single motherhood and neonatal mortality among twins and whether such a linkage varied by race. STUDY DESIGN: Retrospective cohort analysis on 446,570 twin live births (between 24-44 gestational weeks inclusive) in the United States from 1995 through 1998. Neonatal survival was compared between twins of single and those of married mothers for blacks and whites separately using Cox proportional hazards regression that adjusted for the confounding effects of education, parity, adequacy of prenatal care and maternal smoking during pregnancy. The Robust Sandwich Estimator was employed to adjust for intracluster correlation. RESULTS: The rates for neonatal mortality among blacks were 34.9 per 1,000 among married and 43.4 per 1,000 among single mothers. Among whites, the rates were 20.6 per 1,000 for married and 28.9 per 1,000 for unmarried mothers. Neonatal mortality was significantly elevated among white twins of single mothers (Hazard Ratio (HR) = 1.23; 95% Confidence Interval (CI) = 1.14-1.31) and among black twins of single mothers (HR = 1.12; 95% CI = 1.01-1.25). However, when gestational age was adjusted for, the association between single motherhood and neonatal mortality disappeared. CONCLUSION: Single motherhood was a risk factor for neonatal mortality among twins, and the disparity in survival was more accentuated among whites. The association between single motherhood and neonatal mortality was explained by the preponderance of preterm births among twins of unmarried gravidas. Our findings reinforce the importance of future research to develop and test interventions that will decrease the incidence of preterm birth.