EFFECT OF PROGESTERONE AND OESTROGEN ON PREGNANCY AND EMBRYONIC MORTALITY IN ADULT MICE FOLLOWING SUPEROVULATION TREATMENT

Abstract

SUMMARY: The effects of exogenous oestrogen and progesterone on implantation and foetal mortality were studied in mice following induced superovulation with gonadotrophins. Short-term treatment with progesterone during early pregnancy did not influence implantation or foetal mortality, but 2 mg daily from days 2 to 12 reduced the number of embryos that implanted and increased foetal mortality after implantation. These effects of progesterone were more severe when few embryos were implanted. Oestradiol benzoate (OB), given after mating, reduced fertility by decreasing the proportion of mice with implanted embryos, causing cornification of the vagina in many mice during pregnancy. Administration of progesterone with OB did not alleviate these effects. Administration of OB before superovulation, or lengthening the interval between the injections of PMS and HCG in order to extend the period of uterine stimulation by endogenous oestrogen, interfered with ovulation in some mice. Approx. one-quarter of the mice given oestrogen had cornified vaginal smears during early pregnancy. Both treatments decreased the numbers of mice with implanted embryos.