In vitro suppression of murine blastocysts growth by sera from women with reproductive disorders.

Early mouse embryos at the two-cell stage were cultured in medium supplemented with sera from women with primary and secondary multiple spontaneous abortions and with long term unexplained infertility as compared to sera obtained from normal fertile women and pooled human male sera. On the basis of microscopic observation and uptake of 3H-thymidine we report a relationship between reproductive histories and the presence of a serum embryo inhibition factor in eight of ten sera samples from women with primary habitual abortions, six of ten sera from women with secondary habitual abortions, and ten of ten sera from women with unexplained infertility. This activity occurs independently of positive maternal antipaternal lymphocytotoxicity. Fractionation of serum samples by ammonium sulphate precipitation, resulted in removal of the embryo-inhibition factor with the IgG fraction in four of five primary habitual abortion cases and in two of five secondary habitual abortion patients, but not in the case of unexplained infertility. We propose that the appearance of such inhibition factor may be of relevance in the etiologies discussed in this paper and may possibly provide the basis for a new classification of idiopathic spontaneous habitual abortions, i.e. positive or negative for the embryo inhibition factor.