Evaluation of normal gestational sac growth: appearance of embryonic heartbeat and embryo body movements using the transvaginal technique

A cross-sectional transvaginal ultrasound study was conducted in 137 normal pregnancies with gestational ages ranging from 5-12 weeks. Several biometric measurements were obtained throughout pregnancy, including the three diameters of the gestational sac, the crown-rump length, and the yolk sac. In addition, the appearance of the embryo heartbeat and embryo body movements were evaluated. Linear relationships were found between the mean gestational sac diameters and gestational age (r = 0.911; P less than .00001) and between mean gestational sac growth and crown-rump length growth (r = 0.926; P less than .0001). A gestational sac could be identified at 5 weeks' gestation; embryo heartbeat was imaged when the mean gestational sac diameter measured 2 cm, and embryo body movements could be seen when the mean gestational sac diameter reached 3 cm. In the present study, embryo heartbeat was identifiable after 6 weeks and 4 days with a sensitivity of 100%, specificity of 93.1%, positive predictive value of 96.9%, and negative predictive value of 100%. The embryo body movements, which were absent before 7 weeks' gestation, were observed after 8 weeks' gestation with a sensitivity of 100%, specificity of 92.8%, positive predictive value of 94.3%, and negative predictive value of 100%. With identification by transvaginal sonographic evaluation, the following can serve as markers of normal embryo growth: a mean gestational sac diameter greater than 2 cm in the presence of the embryo heartbeat, or a mean sac diameter measurement greater than 3 cm in the presence of embryo movement.