Effects of oligohydramnios on the histological structure of full term placenta

Abstract

The present study is an attempt to define the histological effects of oligohydramnios on the structure of the full term human placenta and to correlate the histological changes found with the severity of the condition.The study was conducted in Mosul city from March 2006 to August 2006, the placentae were obtained from 40 pregnant women diagnosed by ultrasound to have oligohydramnios and other 40 pregnants having an ultrasound revealing normal amount of amniotic fluid (as a control group). From the group with oligohydramnios 15 pregnants diagnosed to have a history of preeclampsia according to their clinical manifestations of elevated blood pressure (more than 140/90 mmHg), edema of the face and hands and their urine examination for proteinuria (more than 300 mg of protein in a 24 hr.specimen correlated with +1 or +2 reading on dipstick ), other 15 pregnants with oligohydramnios were post mature and their gestational age prolonged beyond 41 weeks according to their last menstruation and their ultrasound.The remaining 10 pregnants with oligohydramnios were discovered to have small-for gestational age babies with birth weights less than 2500gm.All the pregnant diagnosed to have oliugohydramnios showed the same placental histological appearance whatever the underlying cause. The specimens of the placenta were prepared for histological examination then the sections were stained with various histological stains (including Haematoxylin and Eosin) and some histochemical stains (such as PAS) then statistical analysis of the clinical observations and histological findings was done to define the significance of each finding (using Chi-square test and Z-test of two proportions) and to correlate the incidence of these changes with the severity of oligohydramnios.The study showed that oligohydramnios is strongly associated with fetal growth retardation as a result of uteroplacental insufficiency when compared with the control group. On microscopic examination of the placentae pronounced histological changes were noted in the group with oligohydramnion, the incidences of these changes increased with increasing severity of the condition. The characteristic changes include: Excessive syncytial knots, cytotrophoblastic hyperplasia, thickening of the trophoblastic basement membrane, stromal fibrosis, fibrin deposition within the villi and in between the cells of decidua basalis, villous edema, arteriosclerosis of the uteroplacental arteries. There was a decrease in the vascularity of the villi of the placentae of the group with oligohydramnios (by counting the number of the capillaries in the villi) in addition to areas of focal hemorrhage in the intervillous space and decidual cell calcification