New Japanese neonatal anthropometric charts for gestational age at birth

Background: More than 10 years have passed since the previous Japanese neonatal growth charts were published, therefore the aim of this study was to develop an updated set of Japanese neonatal growth charts.

Methods: We used data from the registry database of the Japan Society of Obstetrics and Gynecology from 2003 until 2005. A total of 150,471 singleton live births without stillbirth or severe congenital malformation were enrolled in the preliminary analysis. It was found that the distribution of the 10th centile charts based on these subjects was skewed toward lower birthweight for preterm infants, because of the significantly lower birthweight in the 10th centile in neonates delivered by cesarean section than those delivered vaginally. Therefore, the data of subjects delivered by cesarean section were also excluded.

Results: Finally, 104,748 singleton vaginal births at 22-41 weeks of gestation were used to construct a new set of Japanese neonatal anthropometric charts. The birthweight chart is parity and sex specific. The differences between the Japanese fetal growth chart and the new neonatal birthweight chart were small.

Conclusion: The present new neonatal anthropometric charts may reveal unrestricted growth pattern mimicking fetal growth. Use of these charts may result in recognition of abnormal fetal growth and risk in preterm infants. Further studies are needed to evaluate the risk for adverse neonatal and long-term outcome among small-for-gestational-age infants using these neonatal charts.