Mortality Rate of Japanese Twins and Triplets III. Infant Deaths of Triplets After Birth to One Year of Age

Abstract

The rate of infant mortality of triplet individuals (deaths under one year of age) was computed using 34 sets of triplets born in the first half of 1974. The rates were 8.82%, 9.68%, and 10.34% for the first-, second-, and the third-born triplets, respectively. For males and females the rates were 8.33% and 10.34%, respectively, and the difference was not significant. The rate decreased with gestational age up to 32-35 weeks. For those with heavier weight at birth (≤2,000 g) the rate was lower (0%) than for those with lighter weight (<2,000 g, 8.16%), but the difference is not significant (P = 0.087). Infant mortality rate of triplets decreased with increased monthly expenditure of the household.