Childhood growth of term singletons born after frozen compared with fresh embryo transfer.

Research Question: Is the growth of term singletons born after frozen embryo transfer (FET) comparable to those born after fresh embryo transfer and natural conception up to 5 years of age?

Design: Observational cohort study in an academic medical centre and municipal child health clinics with repeated measurements carried out by medical professionals. Term singletons born after FET (n = 110) and fresh embryo transfer (n = 181) and their matched natural conception controls (n = 543) born in Oulu, Northern Finland, were included. Mean weights, lengths, heights and head circumferences at the ages of 4, 8 and 18 months and 3 and 5 years were compared. At 3 and 5 years, body mass indices were compared.

Results: Childhood growth did not differ between term singletons born after FET, fresh embryo transfer and natural conception, correcting for exact age at measurement and adjusting for maternal body mass index and paternal height.

Conclusions: Similar growth between children born after FET, fresh embryo transfer and natural conception offers reassurance of the safety and feasibility of the steadily increasing use of embryo cryopreservation in assisted reproduction.