This multicenter prospective cohort study in Japan compared anthropometric outcomes (weight, height, BMI, overweight/obesity risk) at age 12 among singleton children conceived via fresh embryo transfer (FreET, n=1,115), frozen-thawed embryo transfer (FET, n=1,341), or natural conception in infertile couples without ART (n=546), with 671 children completing follow-up.
At age 12, adjusted mean weight, height, and BMI did not differ significantly across FreET, FET, and non-ART groups; odds ratios for overweight (BMI ≥23) and obesity (BMI ≥27) were also non-significant. Parental body size and being large for gestational age (LGA) at birth were independent predictors of larger body size and overweight in boys.
High attrition: only 671 of 3,002 eligible children completed follow-up (~22%), raising selection bias concerns. The non-ART comparator was limited to infertile couples, not the general population. Study was conducted in a single country (Japan), limiting generalizability.
Clinicians can reassure families that the larger birth size seen with FET does not appear to persist as excess weight or obesity risk by age 12. Ongoing monitoring through adolescence is still advisable, as long-term data remain limited.
