Placental and spiral artery volume and gray-scale value assessment via 3-dimensional sonography in the second trimester.

Purpose: Extreme placental size has been associated with abnormal pregnancy outcomes. The purpose of this study was to establish normal values for placental and spiral artery volume and gray-scale value as assessed via 3-dimensional (3D) sonography in the second trimester.

Methods: The entry criterion was a documented singleton pregnancy at 14-25 weeks' gestation. Patients with normal pregnancy outcome were stratified into 6 subgroups representing 2-week intervals. Automatic 3D sonographic acquisition of the placental and spiral artery volume and gray-scale value, expressed as a percentage, was obtained.

Results: Out of 199 patients with normal pregnancy outcome, the placental volume was between 77.7 and 213.9 cm(3) and the gray-scale value was between 28.6 and 29.2 cm(3) (depending on gestational age). The spiral artery volume adjacent to placenta was between 47.9 and 108.7 cm(3), and the gray-scale value was between 27.5 and 29.5 cm(3). Statistical analysis in each subgroup of patients revealed a significant difference between placental and spiral artery volumes but no difference when the gray-scale value was compared.

Conclusions: We defined normal placental and spiral artery volume and gray-scale value in the second trimester of normal pregnancy using 3D sonography.