ABSTRACT
From a teleological perspective, the primary purpose of the human endometrium is to create an advantageous environment for blastocyst implantation and development. The seemingly energy inefficient strategy of extensive endometrial turnover and remodeling through cyclical menstruation is a recent evolutionary development restricted to old world primates. Placentation in primates is relatively invasive, with a diffuse admixture of fetal and maternal cells co-existing at the uteroplacental interface. Several pathological conditions of placentation are unique to higher primates, including ectopic pregnancy (where the implantation site is extrauterine) and placenta accreta (where trophoblastic invasion extends excessively, penetrating the uterine myometrium). The placental pathology of the preeclampsia syndrome, which occurs spontaneously in women and baboons (Hennessy et al., 1997), is characterized by unusually shallow invasion and has been a focus of considerable investigation over the past four decades.
