Frozen, fresh embryo transfers yield similar growth outcomes

Elaine Soliven
23 Jul 2019

Children who were born after frozen embryo transfer (FET) showed comparable growth outcomes during their first 5 years of life as those who were born after fresh ET, according to a study presented at ESHRE 2019.

“Knowledge on the childhood growth patterns of these children is still very limited. There is some evidence of catch-down or catch-up growth for FET and fresh ET children, which might have implications on their long-term health,” said lead author Dr Anna Terho from the Department of Obstetrics and Gynaecology at Oulu University Hospital in Oulu, Finland.

This prospective cohort study analysed 291 term (37─42 weeks of gestation) singleton children who were born after FET (n=110) or fresh ET (n=181) between 2006 and 2011 at Oulu University Hospital in Finland. All pregnancy and labour information were gathered from Oulu University. Growth information was taken from the Municipal Child Health Clinic database. Mean weight, length/height, and head circumference as well as body mass index (BMI) were measured at 3 and 5 years of age. [ESHRE 2019, abstract O-036]

After adjusting for age at measurement, maternal parity, and BMI, children in both the FET and fresh ET groups showed similar weight at 3 years (mean, 14,778 vs 14,494 grams; p=0.459) and 5 years (mean, 19,458 vs 19,392 grams; p=0.843).

Mean height was also not significantly different among children in the FET group compared with the fresh ET group at 3 years (95.9 vs 96.5 cm; p=0.315) and 5 years (110.8 vs 111.0 cm; p=0.759).

A subgroup analysis of girls in the fresh ET group was found to be significantly taller than those in the FET group at 3 years of age (p=0.034), but not at 5 years of age.

There were also no significant differences in the mean BMI values of children born after FET or fresh ET at 3 years (16.0 vs 16.0 kg/m2; p=0.918) or 5 years (15.8 vs 15.7 kg/m2; p=0.450).

However, a significant trend towards a slightly larger head circumference was observed among children in the fresh ET group than the FET group at 3 years of age (50.3 vs 50.7 cm; p=0.045), while it disappeared by 5 years of age (51.8 vs 52.0 cm; p=0.272).

“[Nevertheless,] the minor differences found in this study are unlikely to have any clinical significance,” said Terho, who also suggested that “the similar growth [patterns] between FET and fresh ET children gives reassurance of the safety and feasibility of FET treatment, thus enabling widespread use of single-embryo transfer policy”.

“[As] the study groups are limited in size ... this should be taken into consideration when interpreting the results. However, Finland’s unique, prospective, high-coverage, free-of-cost child health clinic follow-up made accurate information available for both groups, adding to the reliability of these results,” Terho noted.

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