Fresh versus frozen embryo transfer has no effect on childhood weight

Infants born after fresh versus frozen embryo transfer had no significant difference in birth weight or child- hood weight to 3 years, when controlling for maternal characteristics.

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Volume 112, Issue 4, Pages 684–690.e1


Alessandra J. Ainsworth, M.D., Michelle A. Wyatt, M.D., Chandra C. Shenoy, M.D., Matthew Hathcock, M.S., Charles C. Coddington, M.D.



To evaluate the effect of frozen, compared with fresh, embryo transfer on neonatal and pediatric weight and weight gain trajectory.


Retrospective cohort study.


Academic medical center.


Women who underwent fresh or frozen embryo transfer at the Mayo Clinic from 2010 to 2014. All included embryo transfers resulted in a singleton live birth. Children were followed from birth to at least 18 months. When possible, growth was evaluated to 5 years of age.


Fresh versus frozen embryo transfer.

Main Outcome Measure(s)

Propensity score methodology was used to balance the two groups by maternal characteristics and gestational age before evaluating outcomes. Each infant and childhood growth measurement was compared between the two groups.


Of the 136 women, 87 underwent a fresh embryo transfer and 49 underwent a frozen embryo transfer. Birth length and head circumference were significantly different in infants delivered after fresh versus frozen embryo transfer. There was a statistically significant difference in birth weight between infants born after fresh versus frozen embryo transfer. However, this difference did not persist when adjusted for gestational age, sex, and maternal factors. Childhood growth measurements including age- and sex-specific weight, and body mass index percentiles were not significantly different between groups.


This study confirmed an association of frozen embryo transfer and increased birth weight, but the association did not persist when controlling for confounding maternal factors. We found no effect of fresh versus frozen embryo transfer on neonatal weight and childhood weight gain trajectory.

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Fertility and Sterility

Editorial Office, American Society for Reproductive Medicine

Fertility and Sterility® is an international journal for obstetricians, gynecologists, reproductive endocrinologists, urologists, basic scientists and others who treat and investigate problems of infertility and human reproductive disorders. 


Go to the profile of Samuel Santos-Ribeiro
about 2 years ago

Very interesting take on the neonatal/child weight in fresh versus frozen embryo transfers issue. Indeed, the main concern is whether the known differences in terms of birth weight between these strategies are an early sign of potential health issues for these individuals later on in life. Of course, as the authors mention, it may still be too early for us to feel completely safe and make any definitive conclusions, especially given the limited sample size of the study. Still, this is a good first effort on an issue for which the answer, I guess, only time will tell...