Hazard Analysis of Mortality Among Twins and Triplets in the United States: From 20 Weeks Gestation Through the First Year of Life

Infant mortality is viewed as an important indicator of the health and social conditions of a population. However, the infant mortality rate in the United States is estimated to be much lower than those of other developed nations. This dissertation analyzes the hazard of fetal and infant death for twins and triplets in the United States between the years of 1995 and 2000. This dissertation had two main objectives: first, to examine the effects of the birthweight and gestational age on the hazards of fetal, neonatal, postneonatal, and infant death; and second, to better understand the timing of mortality among multiples during their early life. I show that after controlling for relevant characteristics of the mother and child, gestational age and birthweight significantly influence the hazard of mortality for twins and triplets.
The major finding in this dissertation shows that there is a higher hazard for twins than triplets. The unexpected higher hazard of mortality for twins compared to triplets may well be due to the social and demographic characteristics of parents of twins and triplets, particularly the possible use of Assisted Reproductive Technologies.