Implantation, Maternofetal Exchange and Vascular Relationships

Abstract

Implantation is the mechanism by which the blastocyst establishes itself in the uterus, and the trophectoderm develops an intimate relationship with the uterine epithelium (Parr and Parr 1989; Denker 1993). This process is easily disrupted and most early pregnancy loss occurs during this time (Wilmut et al. 1986). The process can also be suspended (`delay of implantation, embryonic diapause ') at this stage, which serves to reduce the metabolic load on a lactating mother and to ensure that birth occurs at the most advantageous season (Enders and Given 1988; Given and Enders 1989). During diapause, progesterone secretion must be maintained and implantation can be reactivated by a pulse of estrogen in rodents or LIF secretion controlled by day length in mustelids (Lopes et al. 2004).