[Obesity affects the chances of birth after frozen-thawed blastocyst transfer]

Both the number of frozen-thawed embryo transfers and the incidence of obesity have increased sharply in recent years in Assisted Reproductive Technology (ART) centers. The objective of our study is therefore to evaluate the impact of female obesity on pregnancy outcomes for frozen-thawed embryo transfer at blastocyst stage.

This is a single-center retrospective study conducted between January 1, 2016, and December 31, 2019, in our Assisted Reproduction Center in Calais. All consecutive cycles of frozen embryo transfers at blastocyst stage with artificial cycle were included. A total of 296 cycles could be included corresponding to 220 cycles realized in normal Body Mass Index (BMI) patients (18.5-24.9kg/m²) and 76 in obese patients (BMI≥30kg/m²).

Live birth rates and implantation rates were significantly lower in obese patients compared with patients with a normal BMI (respectively 9.2 % vs. 22.3 % and 10 % vs. 20.8 %, P=0.01 and P<0.01).

Therefore, our study showed that obesity is associated with a lower rate of live birth and implantation following frozen-thawed blastocyst transfers in artificial cycles. This could be explained by different factors that can be both embryonic and/or extra-embryonic.