Morphometry of the basal plate superficial uteroplacental vasculature in normal midtrimester and at term

Uteroplacental (UP) vascular arterial pathology has been associated with pregnancy complications. UP arterial structure has been characterized in placental bed biopsies, at the decidual-myometrial junction. Basal plate UP arteries, which are delivered with the placenta and thus routinely available, are not well characterized. We compared basal plate UP arterial segment morphometry in cases of elective termination of a clinically normal pregnancy at 11 to 24 weeks and of term birth. This study was done in a community-based obstetric service in New York City. UP arteries were identified in placentas of 20 midtrimester (MT) cases and 17 term (TERM) cases. We measured 336 UP artery cross-sections from 46 TERM and 290 MT cases. The basal plate UP artery path length was calculated as the distance between (x,y) coordinates of estimated centers of lumen cross-sections. Basal plate thickness near UP arteries, UP artery cross-sectional areas, vascular luminal eccentricity, and radial standard deviation were directly measured off digital images. Nonparametric and parametric methods compared groups, with P < 0.05 considered statistically significant. In TERM cases, the basal plate thickness near UP arteries was 1.8-fold thinner (P = 0.002) and mean basal plate path lengths were 2.13-fold shorter (P < 0.0001) than in MT cases. Mean TERM UP artery cross-sectional area was 3.15-fold larger, the major axis was 1.95-fold larger, and the minor axis was 1.75-fold larger than in MT arteries (P = 0.001 to 0.008). Our data demonstrate that basal plate UP arteries (delivered with the placenta) are less tortuous, with shorter path lengths and larger areas as gestation advances. Normative morphometric data may allow improved diagnostics of placentas from complicated pregnancies.