INTRAUTERINE GROWTH RESTRICTION WITH ABSENT END-DIASTOLIC FLOW VELOCITY IN THE UMBILICAL ARTERY IS ASSOCIATED WITH MALDEVELOPMENT OF THE PLACENTAL TERMINAL VILLOUS TREE

OBJECTIVE: Our purpose was to evaluate the structure of placental term inal villi and their capillaries in pregnancies complicated by intraut erine growth restriction with absent end-diastolic flow velocity in th e umbilical artery. STUDY DESIGN: Glutaraldehyde-perfusion-fixed villo us tissue and a plastic cast of the vessels in at least two cotyledons were prepared from 10 cases with intrauterine growth restriction and 9 gestational age-matched control placentas. The structure and dimensi ons of 20 terminal capillary loops per cast were determined by scannin g electron microscopic examination, and their appearances were correla ted with the peripheral villi of the perfusion-fixed villous tissue.RE SULTS: Capillary loops in the growth-restricted cases were sparse in n umber and significantly longer than in the control cases (218 mu m [72 ] vs 137 mu m [30], mean and SD, p < 0.05). They exhibited fewer branc hes (4.0 [1.9] per loop vs 6.1 [2.2], p < 0.05) and a majority of loop s were uncoiled (79% vs 18%, p < 0.05). The villous tissues from the g rowth-restricted cases demonstrated elongated villi, consistent with t he cast findings. The trophoblast surface was wrinkled and in some are as covered by fibrin plaques. CONCLUSIONS: The terminal villous compar tment of the placenta appears to be maldeveloped in preterm intrauteri ne growth restriction pregnancies where absent end-diastolic flow velo city is demonstrated in the umbilical artery before delivery. These fi ndings are consistent with an increase in fetoplacental vascular imped ance at the capillary level and may account for the impaired gas and n utrient transfer in this disorder.