a1 UZ Gasthuisberg, Katholieke Universiteit Leuven, Leuven, Belgium
The establishment of a pregnancy depends upon mechanisms of forming close contacts between embryonic/fetal and maternal tissues. The starting point is the attachment of the blastocyst to the uterine wall, and this critical step is followed by a series of different morphogenetic events leading to placentation. These processes depend on the invasive properties of extra-embryonic trophectoderm-derived cells that show their highest expression in species with haemochorial placentation, i.e. Insectivores, rodents, and primates including the human. In this review we will concentrate upon the human with occasional reference to other species.
c1 R Pijnenborg, Department of Obstetrics and Gynaecology, UZ Gasthuisberg, Katholieke Universiteit Leuven, B3000 Leuven, Belgium.