Histomorphological features of chorionic villi at 10-14 weeks of gestationin trisomic and chromosomally normal pregnancies

This study examines histomorphometric features in chorionic villi obtained by chorionic villus sampling (CVS) at 11-14 weeks of gestation from 124 ong oing pregnancies (38 with trisomy 21, 14 with trisomy 18, 11 with trisomy 1 3 and 61 chromosomally normal controls). In the trisomy 21 group there was an inverse relationship between fetal nuc hal translucency thickness (NT) and villus diameter and number of capillari es per villus cross-section. In about half of the cases there was perivillo us fibrinoid present, and the amount of this increased with gestation. Comp ared to the chromosomally normal group, in trisomy 18 the villus diameter w as smaller and the number of capillaries per villus cross-section was reduc ed. In the trisomy 21 group, villi had an increased percentage of two layer ed trophoblast present and an increased proportion of villus capillaries wi th nucleated red blood cells present. In all three trisomies, but particula rly in trisomies 18 and 13, both the amount of basophilic stippling of the basement membrane and the proportion of cases with stippling was increased. These results provide data on the possible mechanisms of increased fetal N T and on abnormal placental development in fetal trisomies. (C) 2000 Harcou rt Publishers Ltd.