Determinants of pregnancy rate in the donor oocyte model: a multivariate analysis of 450 frozen-thawed embryo transfers

Abstract

Background: Conflicting results have been published about the determinants of pregnancy after oocyte donation (OD). We used the OD model to determine predictive factors of pregnancy in the recipient after frozen-thawed embryo transfer (FTET) in a specific series where all the embryos were cryopreserved without any prior selection for fresh transfer.

Methods: We report a retrospective study in a university tertiary care center. Multivariate analysis and logistic regression were used to identify predictive factors of pregnancy in a series of 450 OD FTET cycles in 198 infertile women between January 1992 and December 2006.

Results: The mean (+/-SD) recipient age was 35.7 (+/-4.5). Impaired ovarian function was the main indication for OD. The mean +/- SD (range) number of embryos transferred was 1.65 +/- 0.5 (1-3). Overall clinical pregnancy, implantation and delivery rates were 30, 18 and 23%, respectively. After univariate analysis, pregnancy rates were significantly higher in recipients under 35 years, in women with a body mass index (BMI) <30 kg/m(2), in women with an endometrial thickness of > or =8 mm, in amenorrheic women and in women not receiving pituitary down-regulation before endometrial preparation. Using multivariate analysis, the BMI, endometrial thickness and the use of pituitary down-regulation were independent predictors of pregnancy, regardless of age.

Conclusions: This study supports that endometrial thickness of <8 mm, obesity and the use of GnRH analogue pituitary down-regulation before endometrial priming negatively impact pregnancy rates, independently of the recipient's age.