The following is a summary of “Clinical and laboratory parameters associated with cycle outcomes in patients undergoing euploid frozen blastocyst transfer,” published in the June 2023 issue of Reproductive BioMedicine Online by Vidales et al.

Which factors influence the clinical pregnancy rate (CPR) and live birth rate (LBR) in cycles of euploid frozen embryo transfer (FET)? From November 2016 to December 2020, a retrospective observational study involving 1,660 eFET cycles with 2,439 euploid blastocysts. The influence of clinical and laboratory parameters on the clinical pregnancy rate (CPR), biochemical miscarriage rate (BMR), clinical miscarriage rate (CMR), and live birth rate (LBR) was evaluated. CPR per transfer was 63.4%, and LBR was 51.0%. 

CPR and LBR were markedly increased when double embryo transfer (DET) was performed (71.6% versus 57.7%, P<0.001 and 55.2% versus 49.9%, respectively, P = 0.016). However, pregnancy loss was considerably higher in the DET group than in the control group (28.8% versus 22.2%, P = 0.02). The classification of patients by body mass index (BMI) revealed no differences in CPR, but CMR was reduced (P<0.001), and LBR was higher (P = 0.031) in the regular BMI group. The natural cycle protocol was associated with a lower CMR (P<0.001) and pregnancy loss (P<0.001), followed by a higher LBR (57.6%, 48.8%, 45.0%, P = 0.001) in comparison to the hormonal replacement protocol and stimulated cycle. The day of trophectoderm biopsy influenced CPR (P<0.001) and LBR (P<0.001), but there were no differences in BMR, CMR, or pregnancy loss. 

Multivariate analysis revealed that day 6/7 embryos had lower pregnancy probabilities; overweight and obesity hurt LBR; and natural cycle improved LBR (adjusted odds ratio of 1.44, 95% CI of 0.519–0.802). CPR was influenced by the biopsy day, while BMI and endometrial preparation protocol were associated with LBR in FET. DET should be discouraged because it increases the risk of miscarriage. Even though a euploid blastocyst is transferred, women with a higher BMI are at a greater risk of pregnancy loss and have a decreased LBR.

Source: sciencedirect.com/science/article/abs/pii/S1472648323001530