Epidemiology of Birth Defects in Very Low Birth Weight Infants in Japan.

OBJECTIVE: To evaluate the mortality and morbidity of very low birth weight (VLBW) preterm infants with birth defects in Japan.

STUDY DESIGN: Data were collected prospectively for infants weighing <1,501 grams and born at <37 weeks of gestation admitted to centers of the Neonatal Research Network of Japan during 2003-2016. We compared outcomes of infants with and without birth defects using Pearson chi-square test, Wilcoxon rank sum test, log-rank test, nominal logistic regression analysis, and stratified analysis by birth defect subgroups. This study was approved by the Ethics Committee of Kyoto University Graduate School and Faculty of Medicine.

RESULTS: Among 57,730 VLBW preterm infants, 3,557 infants (6.2%) were born with birth defects. Chromosomal abnormalities, congenital heart defects, and congenital malformation of the digestive system were the most common categories. Among diseases, trisomy 18, Down syndrome, and cleft palate were the most prevalent. There were significant differences between perinatal characteristics of infants with and without birth defects. Most categories of morbidity occurred more frequently in infants with birth defects compared with those without birth defects. The adjusted odds ratio for mortality during the NICU admission was 10.6 (95%CI: 9.5-11.7) for infants with birth defects. A stratified analysis identified birth defect categories with good, moderate, and poor prognoses.

CONCLUSIONS: This detailed information about mortality and morbidity of preterm VLBW infants with birth defects should be useful for genetic counseling as well as prenatal and neonatal care, with the limitation that we lacked information about the timing of diagnosis, abortion or stillbirth.