Figure 1.

The growth of diapausing blastocysts is reversibly arrested before implantation into the uterus. (a) A diapausing blastocyst (arrowhead) is shown in contact with the uterine luminal epithelium (LE). Note the loose fibroblastic morphology of the stroma (S) underlying the luminal epithelium. T, the trophoblast of the blastocyst. (b) Implantation after diapause starts with the luminal epithelium adjacent to the trophoblast of the blastocyst undergoing apoptosis as the trophoblast cells start to invade the uterus. After implantation, the stroma has undergone massive proliferation and differentiation to form the decidua (D).