Impact of quantitative parameters, such as number of retrieved oocytes, number of transferred embryos and availability of surplus embryos for cryopreservation, on clinical pregnancy rates in ART

Abstract

Objective: To estimate the impact of quantitative parameters such as number of retrieved oocytes, number of transferred embryos and availability of surplus embryos for cryopreservation on clinical pregnancies in assisted reproductive technology (ART).Design: We used the database of fertility clinic on in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) treatment cycles from year 2000 to 2010. Follicular fluids containing oocyte–cumulus complexes were recovered by a single lumen follicle aspiration needle, and IVF or ICSI procedure was used depending on infertility indications. Fertilization determination was performed on the second day. Zygotes were transferred into fresh medium and cultivated until the embryo transfer procedure. According to morphological criteria, the best quality embryos were transferred into uterus on the second or third day. Surplus embryos were frozen by slow freezing or by vitrification. We evaluated only clinical pregnancies that were diagnosed by ultrasonography.Patients: We allocated all 1161 women cohort into three age groups: 671 women were <35; 397 were 35–40 years old and 93 women were >40. Indications for IVF treatment were as follows: mechanical factor (436 cases), male infertility (361 cases), idiopathic infertility (129 cases), endometriosis (78 cases), immunological infertility (14 cases), anovulation (28 cases), and other indications (28 cases). There were no data about the cause of infertility of 87 patients. The stimulation protocol was composed from gonadotropin hormone stimulation with antagonist or agonist supplementation. The triggering of luteinizing hormone (LH) surge was performed by recombinant human chorionic gonadotropin (hCG). The clinical pregnancy rates were: 42.2% (283/671) for women <35, 31.2% (124/397) for women 35–40-year-old and 16.1% (15/93) for women >40.Interventions: All materials and methods that we used were based on results from our daily practice in IVF clinic and have no experimental design.Main outcome measures: We evaluated clinical pregnancies in terms of the number of obtained oocytes, the amount of transferred embryos and the availability of surplus embryos for freezing. The number of retrieved oocytes was divided as follows: 1–5 (group I); 6–10 (group II); ≥11 (group III). The number of transferred embryos was from 1 to 3. Cases at which cryopreservation of embryos was not performed were evaluated as well.Results: For women <35 and 35–40 years old, the highest percentage of pregnancies was achieved when 11 and more oocytes were obtained. Differences in women under 35 between groups were statistically significant. Statistically significant differences in clinical pregnancies depend on the number of transferred embryos in the age groups of <35 and 35–40. Women <35 and 35–40 years old, with the availability of surplus embryos for freezing, had better chances for pregnancy compared with women, who had no excess embryos for freezing.Conclusions: The number of obtained oocytes, the number of transferred embryos and the availability of surplus embryos for freezing may serve as predictors of pregnancy rates in ART.