EFFECT OF AN IUD ON IMPLANTATION AND THE DECIDUAL REACTION IN DIFFERENT STRAINS OF MICE

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Abstract
In mice of 4 genetically different strains, a silk suture was placed in one of the uterine horns while the remaining horn was left untreated. When the females were mated, no evidence of implantation was found in the threaded horn. In the contralateral horn, implantation occurred in only about 50% of the mice and embryonic mortality was increased. In some females the uterine horns were scratched 3 days after sterile mating to evoke a decidual reaction. Deciduomata were inhibited completely in the threaded horn, and partially in the control horn. The 4 strains differed both in the proportion of females with implantations in the control horn and in the degree of decidual growth inhibition. The effects of an IUD on implantation and on decidual reaction were correlated. When an IUD was removed after plug formation, but before the blastocysts entered the uterus, implantation occurred in both horns in about 40% of the females. These results suggest that an IUD in mice may exert its effect on fertility by impairing the uterine sensitivity to mechanical stimuli at the time of implantation and that the extent of this action is genetically determined.