First-Trimester Ultrasound Volumetry

Measurement Techniques and Potential Application in the Prediction of Pregnancy Complications

Kwok Yin Leung; Teresa Ma; Betty YT Lau; Min Chen


Expert Rev of Obstet Gynecol. 2012;7(4):379-386. 

In This Article

Gestational Sac Volume

The gestational sac consists of the amniotic cavity and the exocelomic cavity in the first trimester. GSV is commonly measured using the VOCAL method with a 30° rotation angle.[9,33] Intraobserver variability was excellent, with an average difference between measurements of 0.5 cm3.[9] GSV can be measured with reliably in VR, but the results were on average 19.8% smaller than the GSV calculated using the ellipsoid formula.[55]

There was a high correlation between GSV and GA or CRL.[1,9,16] Mean GSV increased from 8.50 cm3 at 7 weeks to 44.35 cm3 at 10 weeks,[15] and 69 ml at 11 weeks to 144 ml at 13 + 6 weeks.[20] GSV increased from 5.00 to 50.28 cm3 for a CRL increase from 0.9 to 4 cm.[9]

GSV is closely related to amniotic fluid volume, which is an ultrafiltrate of maternal plasma. GSV may reflect uteroplacental function in the first trimester,[56] and may potentially have predictive value for adverse pregnancy outcomes.[24]


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