Apoptosis in human chorionic villi and decidua during normal embryonic development and spontaneous abortion in the first trimester.

To investigate possible apoptotic changes, the cleavage of DNA in human chorionic villi and decidua was examined during the first trimester of pregnancy by molecular biochemical techniques. Very limited but detectable cleavage of DNA was recognized in the chorionic villi and decidua in normal pregnancy. The characteristic apoptotic breakdown of DNA was recognized in the chorionic villi and decidua in cases of spontaneous abortion. Quantitative analysis of low molecular weight fragments of DNA revealed a significant increase in cases of spontaneous abortion compared to those in normal pregnancy. However, the extent of apoptosis was not correlated with either urinary levels of human chorionic gonadotropin (hCG) and/or gestational age. An analysis in situ revealed cells undergoing apoptosis in the cytotrophoblast in normal pregnancy, and apoptotic cells were predominant in the syncytiotrophoblast in cases of spontaneous abortion. It is shown that apoptosis occurs in the human conceptus during the first trimester of normal pregnancy and is greatly intensified in cases of spontaneous abortion. In addition, the results indicate that apoptosis might play a critical role in embryonic development and wastage in humans.