Eur J Obstet Gynecol Reprod Biol. 2026 Jun 4;324:115227. doi: 10.1016/j.ejogrb.2026.115227. Online ahead of print.
ABSTRACT
OBJECTIVE: To investigate whether the increased birth size linked to frozen-thawed embryo transfer (FET) compared with fresh embryo transfer (FreET) and natural conception persists at 12 years of age.
METHODS: This multicenter prospective cohort study included singleton children born between 2008 and 2009 at 23 JISART-affiliated facilities in Japan. Children conceived via assisted reproductive technology (ART) (FreET and FET) were compared with those conceived naturally by couples who are infertile without ART. Overweight and obesity were defined according to the International Obesity Task Force criteria (overweight: body mass index [BMI] ≥ 23, obesity: BMI ≥ 27). Analyses were performed using analysis of covariance and multiple regression, adjusting for gestational age, maternal age, parity, small/large for gestational age (SGA/LGA), parental body size, education, and infertility duration. Logistic regression was used to assess the risk of overweight/obesity.
RESULTS: Of 6,434 children initially contacted, 3,002 eligible singletons (1,115 FreET, 1,341 FET, and 546 non-ART) were included in the birth cohort, with 671 (331 boys, 340 girls) finally enrolled. The adjusted mean weight, height, and BMI did not differ among the FreET, FET, and non-ART groups. The odds ratios for overweight and obesity also showed no significant group differences. Parental body size was associated with child anthropometry, and LGA at birth independently predicted a larger body size and being overweight in boys.
CONCLUSIONS: At 12 years, body size and overweight risk were comparable among the three conception groups (FreET, FET, and non-ART groups). We found no statistical evidence that the FET-associated increase in birth size persisted into early adolescence. Continued follow-up during adolescence is warranted.
PMID:42251806 | DOI:10.1016/j.ejogrb.2026.115227
