Gestational Age and Neurodevelopmental Delay in Term Births at 6 and 12 Months: The Japan Environment and Children’s Study (JECS)

In the recent years, a high risk of developmental delay not only in very low birth weight infants and late preterm infants but also in early term infants (37–38 weeks) have increasingly been reported. However, in Japan, there are virtually no studies regarding the development delays in early term infants.

This study used the data from the Japan Environment and Children’s Study (JECS), a birth cohort study conducted in Japan. Data were selected for analysis from the records of 104,065 fetal records. The risk of neurodevelopmental delays at 6 months and 12 months after birth was evaluated using multivariate analysis for infants of various gestational ages, using the 40th week of pregnancy as a reference value. Neurodevelopment was evaluated at 6 months and 12 months after birth using the Ages and Stages Questionnaires, Japanese translation (J-ASQ-3).

The proportion of infants born at a gestational age of 37 to 38 weeks who did not reach the J-ASQ-3 score cutoff value was significantly higher in all areas at both 6 months and 12 months after birth, when compared to that of infants born at 40 weeks. The odds ratio decreased at 12 months after birth compared to that at 6 months after birth.

Early term infants in Japan are at an increased risk of neurodevelopmental delay at 12 months after birth.