ABSTRACT
OBJECTIVE: The purpose of this study is to verify the correlation between gestational sac volume (GSV) from automatic tracing mode the VOCAL-imaging program and gestational age and to construct the nomogram of gestational sac volume as the new biometric parameter in early pregnancy. METHODS: The cross-sectional study has been conducted in 242 uncomplicated singleton pregnancies. 47 cases were excluded due to early pregnancy failure, fetal malformations, elective abortion, age discrepancy, etc. In 195 uncomplicated singleton pregnancies from 5 to 12 weeks' menstrual age, gestational sac volume, mean sac diameter and crown-lump length were measured for the assessment of gestational age. Gestational sac volumetry was carried out with automatic method and manual method of the VOCALTM (Virtual Organ Computer- aided AnaLysis) for the comparison between two methods. The collected data were analyzed for mean, standard deviation, 90% reference interval, 5th, 50th and 95th percentiles of gestational sac volume, mean sac diameter and CRL, and the nomogram were constructed. RESULTS: Polynomial regression analysis demonstrated the statistically significant positive correlation between gestational age and gestational sac volume by automatic tracing mode (R2 0.826, p<0.001), gestational sac volume by manual tracing mode (R2 0.844, p<0.0001), mean sac diameter (R2 0.763, p<0.0001) and crown-lump length (R2 0.950, p<0.0001). The 5th, 50th and 95th percentiles of the gestational sac volume were calculated and the nomogram was tabulated. In determining gestational age, the standard deviation (SD) of gestational sac volume by automatic tracing mode is 5.6 days, the SD of gestational sac volume by manual tracing mode is 5.2 days and the SD of MSD is 6.6 days. CONCLUSION: we can conclude that three-dimensional GSV with automatic tracing mode of the VOCAL-imaging program can be used as the new biometric measurement in determining gestational age. Gestational sac volumetry with automatic tracing mode of the VOCAL-imaging program have been proven available and convenient method and it can be recommended in 5-7 weeks' of gestation, when CRL is not clearly visualized.