A Method for Quantifying Birthweight Discordance in Quadruplets and Potential Use in Predicting Early Mortality

Abstract

We describe an approach to quantify birthweight discordance in quadruplets and assessed its potential use in predicting infant mortality. Retrospective cohort study on quadruplets delivered in the United States from 1995 through 2000 inclusive. The main outcome measures were infant, neonatal, and postneonatal mortality. A total of 2692 quadruplet live births (673 complete clusters) with complete information on gestational age, birthweight, and survival within the first year. Of the total 673 quadruplet clusters, discordance occurred in 180 sets (26.7%). The predominant discordant type was a single discordant individual within a cluster (177 sets or 99.8%), whereas only three sets (0.2%) recorded up to two discordant quadruplets within a cluster. The period of pronounced risk for the occurrence of birthweight discordance was between 28 and 35 gestational weeks. Discordant individuals exhibited elevated risk for infant (adjusted odds ratio [aOR] = 2.1; 95% confidence interval [CI], 1.4 to 3.0), neonatal (aOR = 1.8; 95% CI, 1.2 to 2.6), and postneonatal (aOR = 2.9; 95% CI, 1.1 to 8.4) mortality. After adjusting for small for gestational age, the risk for postneonatal mortality among discordant infants quadrupled (aOR = 4.1; 95% CI, 1.5 to 10.8). The population-attributable risks were 18, 20, and 46% for neonatal, infant, and postneonatal mortality, respectively. The new method is predictive of mortality at all stages of infancy. Discordance accounts for 18 to 46% of all quadruplet deaths during infancy in the United States.