Placental vessel morphometry in growth retardation and increased resistance of the umbilical artery Doppler flow

Abstract

Objectives: To study the tertiary-stem villi vessel lumen and wall thickness of placenta in pregnancy complicated with placental insufficiency and intrauterine growth retardation (IUGR), its correlation with the umbilical artery Doppler flow study, and compare with normal and non-IUGR pregnancies.

Methods: Placentas from 45 deliveries (between 28 and 38 weeks) were collected for morphometric study of the tertiary-stem villi vessels. Each pregnancy had clinical suspicion of IUGR and was confirmed by serial ultrasound biometry, HC/AC ratio, and had abnormal umbilical artery Doppler velocimetry (RI). Each placenta was weighed after trimming of the membrane and the cord. Sections of the placenta (4 micron) were stained with hematoxylin and eosin and periodic acid-Schiff reagents. Tertiary-stem villi vessels were identified under a microscope (x40) and morphometric study was performed. Inner and outer circumferences (2.pi.r) were measured, radii (r) were calculated, and vessel wall thickness was determined (outer r - inner r). These findings were compared with the findings from 78 placentas from normal pregnancies (between 28-40 weeks) and 27 placentas from pregnancies with medical complications without IUGR (non-IUGR) and with normal Doppler velocimetry (between 33 and 38 weeks).

Results: Weight of placentas were significantly (P < 0.005) lower in IUGR than the normal and non-IUGR groups. The vessel wall thickness was significantly (P < 0.0001) increased in IUGR group (mean 21.17 +/- 3.16 micron [SD]) compared to normal and non-IUGR groups (mean 13.19 +/- 1.66 micron). With advancing gestational age, the thicknesses of vessel walls in all groups were significantly (P < 0.001) decreased. There was significant (P < 0.001) decrease in lumen circumference in the IUGR group (mean 173 +/- 31 micron) compared to normal and non-IUGR groups (mean 69 +/- 23 micron). Significant (P < 0.001) correlation was observed between the thickness of a vessel wall and the increase in Doppler RI.

Conclusions: Pregnancies with growth retardation are associated with smaller placentas, increase in the thickness of tertiary-stem villi vessel wall, and decrease in lumen circumference. These changes are associated with an increase in the resistance index of the umbilical artery Doppler flow velocimetry.