[Success' determinant variables in assisted reproduction].

OBJECTIVE: To perform a statistical analysis with variables that have influence on pregnancy rates to establish a prognostic factor of each one. PATIENTS AND METHODS: We performed a retrospective, descriptive, and observational study with 240 patients that underwent to IVF-ET program. The analyzed variables were: infertility factor, ovarian stimulation protocol, age of patients, basal hormonal levels, oestradiol preovulatory levels, endometrial characteristics, fertilization rate, number and quality of oocytes, number and quality of embryos, and difficulty of the embryo transfer. RESULTS: The mean age of the patients was 34 +/- 4.42 years old. Tubal and pelvic pathologies were the main infertility cause. During the statistical analysis we observed that the only variables with differences regarding pregnancy were the number of cells in the embryo (7.18 vs 5.9), the fertilization rate (58.3 vs 50.1%), and the number of transferred embryos. With the logistic regression analysis we observed that the number of cells on each embryo had a relative risk of 1.37 (CI 95%; 1.15-1.63), and that the number of transferred embryos had one of 1.63 (CI 95%; 1.10-1.58). CONCLUSIONS: There are many variables that influence the pregnancy rates, but with our results we consider that the embryo quality, its characteristics and the number of transferred embryos could predict better the possibilities of pregnancy in IVF-ET programs.