Effects of Late Preterm Birth on the Incidence of Developmental Delays among Children at 3 Years of Age: A Matched-Pair Case-Control Study

Purpose: To investigate the relationship between preterm delivery and developmental outcomes in children born at 34 36 weeks of gestation (late preterm period). Methods: This study reviewed the cases of singleton late preterm children and full-term (38 40 weeks of gestation) children born at Showa University Hospital. The developmental outcomes at 3 years of age were assessed based on the results of questionnaires sent to the families by mail. In addition, the incidence of developmental delays was compared between the late preterm and full-term children. In the fullterm control group, perinatal characteristics (neonatal gender, Apgar score, Cesarean delivery, birth weight < 10th percentile, birth weight < 3rd percentile) were matched with those of the late preterm cases. We compared categorical variables using Fisher’s exact test. For variables with a non-normal distribution, Welch’s t-test was applied. A p-value of <0.05 was considered to be statistically significant. Results: The rate of return of the questionnaires was 25.9% (121) among the cases and 25.8% (163) among the controls. The frequency of developmental delays was 6.6% among the cases, compared with 4.3% among the controls. Conclusions: Matching the perinatal characteristics of the subjects, the frequency of developmental delays was similar between the two groups.