Evaluation of Placental Volume at 7–10 + 6 Weeks of Pregnancy by 3D-Sonography

The aim of the study was to establish normative data for placental volume (PV) at 7–10 + 6 weeks of gestation using three-dimensional ultrasound (3DUS). The cross-sectional study involved 70 healthy pregnancies between 7 and 11 weeks. The VOCAL (Virtual Organ Computer-aided Analysis) method with a 30° rotation angle and six planes was used for volumetric calculations. Regression models were constructed to assess the correlation between PV and crown–rump length (CRL) adjusted by the determination coefficient (R2). The method proposed by Royston and Wright was used to establish the 2.5th; 10th; 50th; 90th and 97.5th percentiles (percentile = mean + K × SD). The intraclass correlation coefficient (ICC), Bland–Altman graphs and Student’s paired t-tests were used to assess intra- and interobserver variability. PV ranged from 1.7 to 42.6 cm3, with a mean of 13.6 cm3 (±9.4 cm3). There was a strong correlation between PV and CRL; the exponential equation was the model that best expressed the correlation between them (R2 = 0.76). For CRL between 9 and 40 mm, the mean PV increased 10.5 times, while CRL increased only 4.4 times. Inter- and intraobserver correlation were excellent (ICC = 0.979 and 0.971, respectively). Bland–Altman graphs indicated a good reproducibility with a mean intraobserver and interobserver difference of 0.2 cm3 (95% CI: −0.7–1.2 cm3) and −0.2 cm3 (95% CI: −1.3–0.9 cm3), respectively. Reference limits were generated for first trimester PV assessed by 3DUS using the VOCAL method. There is a strong correlation between PV and CRL. Placental volume obtained through this method was highly reproducible.