Current incidence of clinical kernicterus in preterm infants in Japan.

Clinical kernicterus in preterm infants has recently been reported in Japan, diagnosed on the basis of clinical findings during the neonatal and infancy periods. We investigated the incidence of clinical kernicterus in preterm infants <30 weeks gestational age (GA) based on a nationwide survey conducted in 233 certified educational facilities for neonatologists. The numbers of infants admitted and infants who died within 14 days after birth during 2011, and the number of infants who subsequently developed clinical kernicterus, were recorded. A total of 2720 infants were analyzed, representing 59% (2720/4623) of all preterm live births <30 weeks GA in Japan in 2011. Of these, 159 (5.8%) died within 14 days after birth, similar to the national rate. Five infants developed clinical kernicterus in infancy (5/2720, 0.18%). The current incidence of clinical kernicterus in Japan is therefore estimated at 1.8 per 1000 live births <30 weeks GA.