Interest in preeclampsia for researchers in reproduction.

Gestational hypertension/preeclampsia, is a major disease of human reproduction, with 10% of human births being affected. It is due to the failure of extravillous cytotrophoblast to invade the maternal uterine spiral arteries to a sufficient depth at the second physiological invasion around the 14-16th week of gestation, inducing poor vascular exchanges between the mother and the placenta. The rise of blood pressure in the human mother is then a compensatory mechanism to increase the exchanges and try to save the fetus from poor supplies. Indeed, it is only in the late 1970s that a puzzling phenomenon has been described: in human pregnancy, in contrast with other mammals, implantation of the embryo occurs by two physiological invasions of the cytotrophoblast inside the uterine wall: (a) at the beginning of pregnancy after fecundation (like all mammals); (b) then follows an apparent long pause (6-8 weeks) and (c) late at the end of first trimester (14-16th week) of gestation, a second very deep (1/3 of the uterine wall) invasion. This two-wave physiological endovascular trophoblast invasion represents a remarkable immunological placental-maternal interaction. Moreover, preeclampsia which has been considered as 'the disease of primigravidae' during all the XXth century may be in fact associated with new paternity especially in couples conceiving very shortly after the beginning of their sexual relationship. 'Primipaternity', rather than primigravidity, is probably the leading cause of preeclampsia. Comprehension in the near future of the physiological immunological tolerance in normal pregnancies and immunological rejection (preeclampsia) of the second trophoblastic invasion will give the biological clue of this puzzling disease, real plague of human reproduction.