The influence of in-vitro culture versus stimulated and untreated oviductal environment on mouse embryo development and implantation

A prospective randomised study was performed to evaluate stimulated versus natural oviductal environment in comparison with in-vitro culture for the developmental capacity of mouse embryos. Therefore, embryos of superovulated F1 hybrid CBAxC57B1 females were collected at 17, 22, 41 and 46 h after human chorionic gonadotrophin treatment and randomly divided into five groups. They were either transferred immediately to untreated pseudopregnant females, cultured in vitro for 5, 24 or 29 h before transfer, or cultured in vitro for 96 h to blastocysts. The transfers resulted in an impaired implantation (P < 0.001) and a lower numbers of living fetuses (P < 0.001) when embryos had been exposed longer to the stimulated oviductal environment. Similar results were obtained after a longer period of in-vitro culture (P < 0.05). However when embryos were flushed earlier from the superovulated mice and cultured longer in-vitro until the transfer was performed, the implantation rate was improved (P < 0.01). Blastocyst development, however, was better (P < 0.001) when embryos were flushed later. In conclusion, the stimulated oviductal environment impairs the developmental capacity of embryos in comparison with untreated pseudopregnant females. In-vitro culture is also suboptimal but better than the stimulated oviductal environment.