Likelihood of pregnancy after the transfer of embryos derived from follicle aspiration and in vitro embryo production sessions with different relative efficiencies.

The aim of the present study was to evaluate the likelihood of pregnancy of in vitro-produced (IVP) embryos from batches with distinct relative efficiencies. Data were retrospectively analyzed from 605 transvaginal ultrasonic-guided follicle aspiration sessions (OPU) followed by in vitro embryo production (IVEP) and 2456 fresh embryo transfers (ET), performed between 2008 and 2012 in individuals of the Gir (dairy Bos indicus) breed. The OPU and IVEP were performed using standard procedures by a single group of technicians at the same laboratory facility. Records were stratified into quartiles (I to IV) according to the total of cumulus-oocytes complexes (COC) produced per donor, or in percentile ranges (0%-25%, 26%-50%, 51%-75%, and 76%-100%) for endpoints related to COC quality or efficiency of embryo production. Pregnancy per embryo transfer (P/ET) was compared among quartiles or ranges using the chi-squared test. Donors producing a greater number of total COC (quartile I) also had more viable and grade I COC, and a greater number of embryos than donors ranked in quartiles II, III or IV, respectively (P < 0.0001). Nevertheless, P/ET did not differ (P > 0.05) among embryos produced by donors ranked in Quartiles I to IV. Similarly, there was no difference (P > 0.05) in P/ET for embryos derived from OPU sessions with a relatively greater or lesser percentage of viable or Grade I COC. Cleavage and blastocyst rates within each IVEP batch had no effect (P > 0.05) on P/ET. In conclusion, data suggest that there is no relationship among oocyte yield after OPU, or efficiency of IVEP, and the likelihood of pregnancy after ET of fresh IVP embryos.