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

Abstract 

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 42.6cm³, with a mean of 13.6cm³ (±9.4cm³). 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 40mm, 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 0.2cm³ (95% CI: −0.7–1.2cm³) and −0.2cm³ (95% CI: −1.3–0.9cm³), 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.

Keywords: Early placental phase, First trimester of pregnancy, Crown–rump length, Organ volume, Three-dimensional imaging