In vitro fertilization and long-term child health and development: nationwide birth cohort study in Japan.

The aim of this study is to compare long-term health outcomes between IVF-conceived children and non-IVF-conceived children in Japan, in the context of strong recommendation for single embryo transfer. Using data from a nationwide birth cohort linked with perinatal database, this study analyzed 2140 children born in Japan in May 2010. It compared child health and development outcomes up to 9 years of age between IVF-conceived and non-IVF-conceived children (binary exposure). A Poisson regression with robust variance to estimate the risk ratios for the association between IVF and various long-term child health and developmental outcomes. After adjusting for confounding factors, no significant differences were observed between IVF-conceived and naturally conceived children for most outcomes, including hospitalization, obesity, and developmental milestones. IVF-conceived children showed a slightly lower risk of attention problems at 8 years (adjusted Risk Ratio [aRR]: 0.73, 95% CI: 0.53-1.00). In subgroup analyses, IVF-conceived term children and singletons demonstrated reduced risk of cognitive delays at 5.5 years (aRR: 0.31, 95% CI: 0.10-0.96 and aRR: 0.37, 95% CI: 0.14-0.98, respectively).Conclusion: In this Japanese cohort, IVF conception was not associated with adverse long-term health or developmental outcomes. These findings provide reassurance about the safety of IVF, particularly in the context of single embryo transfer policies. Further research is needed to explore specific IVF protocols and subgroups.