Assessment of placental vascularization by three-dimensional power Doppler "vascular biopsy" in normal pregnancies

Abstract

Aim: To describe the evolution of placental vascularization during a normal course of gestation and the blood flow 3D power Doppler indices obtained by "placental vascular biopsy."

Methods: A prospective study was carried out on 99 normal singleton pregnancies from 14 to 40 weeks. Placental vascularization was evaluated by 3D power Doppler ("placental biopsy"). The spherical volume acquired was analyzed using the VOCAL imaging program (Virtual Organ Computer-aided AnaLysis). Three vascular indices, vascularization index (VI), flow index (FI), and vascularization-flow index (VFI), were calculated. Equations and regression coefficients for placental volume and vascular indices (VI, FI, VFI) of the placental biopsy were calculated according to gestational age. Relationships between 3D placental flow indices and fetal growth parameters: biparietal diameter, head circumference, abdominal circumference, femur length, estimated fetal body weight, maximum systolic velocity (US), and resistance index in the umbilical artery (URI) were evaluated by calculating their correlation coefficients.

Results: All 3D Doppler indices had a significant relationship with gestational age. The most significant relationship was observed for FI, and the least significant for VI (r=0.58, r=0.29, respectively; P<0.01 for both). The FI increased linearly with gestation, whereas the VI showed a dispersion of values with a plateau from the 30th week onwards and a decrease from 37th week to the end of pregnancy. The VFI behaved as a combination of both VI and FI indices from which it was derived. All 3D Doppler indices were significantly related to fetal biometric parameters, except VI and fetal weight. A significant correlation was observed between 3D Doppler indices and maximum systolic velocity and URI.

Conclusions: 3D power Doppler technique of placental vascular "biopsy" is an appropriate tool for routine evaluation of the human placental vascular tree during gestation. 3D Doppler indices change as pregnancy progresses and are significantly related with fetal biometry and umbilical artery Doppler velocimetry.