EFFECT OF PROGESTERONE ON THE OVARIES AND EMBRYOS OF MICE IN EARLY PREGNANCY1,2

Abstract

The effects of progesterone injected during early pregnancy in the albino mouse differ from those reported by others for the second half of pregnancy. Daily injs. of 1.0 mg. of progesterone, begun the day of mating, prevent implantation. Implantation occurs if these injs. are delayed until the 2d day after mating. The embryos continue to grow during the period of injs. but die within a few days after progesterone is withheld. The corpora lutea show definite signs of regression. This condition is probably due to an inadequate supply of estrogen. These effects of progesterone on the ovary and embryos in early pregnancy are similar to those reported previously after injs. of desoxycortico-sterone acetate.