PROBLEM: Spontaneous abortions occur in 40 to 50% of pregnancies, but the causes for some abortions, especially those that are recurrent (spontaneous), are still unknown.
METHOD: Following previous studies that demonstrated embryotoxic effects of sera from women with spontaneous abortions in preimplantation mouse embryos, we cultured 10.5-day-old rat embryos in sera from women after spontaneous abortions to look for specific teratogenic effects.
RESULTS: About 50% of the embryos cultured in sera from women after spontaneous abortions were malformed, as compared to 19.1 and 27.1% malformations in embryos cultured in sera from women after a normal delivery and during a normal second trimester of pregnancy, respectively. We divided the sera from women who had spontaneous abortions into high-risk, and low-risk sera. In the high-risk sera from one abortion, we found 74.2% malformed embryos and in the high-risk group from two or more abortions this rate was 81.0%. This is compared to a rate of 17.1 and 10.3% in the low-risk sera, respectively. We have also found lower DNA and protein synthesis in the embryos cultured in high-risk sera compared to those cultured in low-risk and control sera. Transmission electron microscopy examination of yolk sacs cultured in high risk sera showed ultrastructural damage as represented by a lower number of microvilli and a higher number of inclusions in the entodermal cells when compared to controls. Amino acid chromatography of the serum and the concentrations of folic acid and zinc were similar in control and high-risk sera.
CONCLUSION: It seems that the majority of sera from women with unexplained spontaneous abortions are teratogenic to rat embryos in culture. In about two-thirds of these sera the teratogenic factor(s) seem to be present in the IgG fraction.