Neurological development in 36‐month‐old children conceived via assisted reproductive technology: The Japan Environment and Children's Study

PURPOSE: This study aimed to investigate neurodevelopment in children conceived via in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) with several types of embryo transfers. METHODS: We analyzed data for 77 928 children and their mothers included in a Japanese birth cohort study. Among the included children, 4071 were conceived via IVF, while 1542 were conceived via ICSI. Neurodevelopmental delay at the age of 3 years was assessed using the Japanese version of the Ages and Stages Questionnaires, 3rd edition. RESULTS: In the crude model, the odds ratios for developmental delay in 1–4 domains were higher among children conceived via IVF, ICSI, and non‐ART (ovulatory induction or intrauterine insemination) than in spontaneously conceived children. After adjusting for parental background factors and the child's sex, there were no differences in the risk of developmental delay when comparing singletons conceived by IVF, ICSI, or non‐ART and those conceived spontaneously. Higher odds ratios for developmental delay in one domain were observed in singleton girls conceived via IVF when compared with those who were spontaneously conceived. CONCLUSION: Most cases of developmental delay may be associated with multiple pregnancies and factors related to infertility, such as parental age, irrespective of the use of ART.