The impact of ovarian stimulation on implantation and fetal development in mice

TLDR

The study aimed to determine whether superovulation with gonadotrophins impairs oocyte/embryo quality or uterine environment, thereby affecting implantation and fetal development in mice. Embryos from superovulated and control females were transferred into distinct uterine horns of either superovulated or non‑stimulated pseudopregnant recipients. Superovulation reduced embryo blastocyst formation, lowered implantation rates, impaired uterine receptivity, increased post‑implantation fetal mortality, and produced lighter fetuses, indicating that ovarian stimulation compromises both oocyte/embryo quality and the uterine environment.

Abstract

The objective of this study was to evaluate, using an embryo donation model, whether impaired oocyte/embryo developmental competence and/or changes in uterine milieu are responsible for the previously observed adverse effects of superovulation with gonadotrophins on implantation and fetal development in mice. Embryos from superovulated and non-stimulated females were transferred to separate uterine horns within the same superovulated or non-stimulated pseudopregnant recipient mice. Embryo development was impaired as a significantly higher proportion of normal embryos from control donors (61%) were blastocysts on transfer day compared with superovulated donors (41%; P = 0.001). The implantation rate in control recipients was significantly reduced after transfer of embryos from superovulated donors (12%) compared with control donors (25%; P = 0.001). Uterine receptivity was impaired in superovulated recipients. The implantation rate of control embryos was significantly higher in control (25%) than in superovulated recipients (7%; P = 0.001). Transfer of embryos recovered from superovulated donors resulted in significantly higher post-implantation fetal mortality in superovulated recipients (69%) than in control recipients (36%; P = 0.01), and the mean weight of live fetuses was significantly lower for fetuses obtained from superovulated recipients (0.51 g) compared with that of fetuses obtained from control recipients (0.72 g; P = 0.006). Hence, ovarian stimulation appears to impair oocyte/embryo quality as well as uterine milieu.