Morphological changes of the spiral arteries in the placental bed in relation to pre-eclampsia and fetal growth retardation.

The spiral arteries at the level of the decidual-myometrial junction in the placental bed were examined histologically in 93 biopsies. Of these, 23 originated from normal uncomplicated pregnancies, 30 from pre-eclamptic and 40 from otherwise complicated pregnancies. The association of the "physiological changes' of the spiral artery with uncomplicated pregnancy and their absence in pre-eclampsia, as noted by Brosens and others, has been confirmed. In addition, in pregnancies without pre-eclampsia, these changes were significantly more often absent with fetal growth retardation. The hypothesis is put forward that hypertension of pregnancy is a compensatory mechanism to ensure an adequate blood supply to the placenta when the "physiological changes' fail to occur.