Comparison of placental volume in early pregnancy using multiplanar and VOCAL methods

In this study we aimed to compare the multiplanar and VOCAL (Virtual Organ Computer-aided AnaLysis) methods in the evaluation of placental volume during the first trimester of pregnancy. This was a prospective cross-sectional study involving 37 pregnant women between 7 and 10 weeks of gestation. All volumetric measurements were performed by a single examiner using an endocavitary volumetric probe (3D5-8EK). Placental volume was measured on three-dimensional ultrasound by the VOCAL method using 12 degrees and 30 degrees rotational angles and by the multiplanar method using sequential sections of the placenta obtained at intervals of 1.0 mm. Pearson's correlation coefficient (r) was used to evaluate the relation between placental volume and gestational age. The interclass correlation coefficient (ICC), paired Student's t-test (P) and Bland-Altman plot were used to compare both methods. There was a strong correlation between placental volume and gestational age (r=0.791 for VOCAL 12 degrees , r=0.801 for VOCAL 30 degrees and r=0.783 for multiplanar). There was a strong correlation between placental volume measured by the VOCAL 12 degrees and the VOCAL 30 degrees (ICC=0.994, confidence interval [0.998; 0.997]) and the multiplanar methods (ICC=0.991, confidence interval [0.983; 0.995]). First trimester placental volume measurements obtained using the multiplanar and VOCAL methods are concordant.