The present invention provides a method of predicting the probability of a successful pregnancy, either a naturally achieved pregnancy or a pregnancy resulting from an assisted reproductive technology, based on the level of L-selectin ligand expressed by uterine epithelial cells and/or the level of L-selectin expressed by an embryo in vitro. The invention further provides methods of inhibiting cell adhesion between a trophoblast and a uterine epithelial cell. Methods of inhibiting cell adhesion between a trophoblast and a uterine epithelial cell are useful to inhibit pregnancy. The invention further provides methods of assessing in vitro embryo quality. The invention further provides methods of predicting the probability of continued success of a pregnancy during the first 16 weeks of gestation.