Fresh versus frozen embryo transfer has no effect on childhood weight

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.

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.