Chapter 30 - First-trimester pregnancy failure

Summary

The gestational sac (GS) should be used to monitor the sequential sonographic milestones of the early, normal intrauterine pregnancy. GS growth rate, location, appearance, and size can all be used as helpful indicators when assessing pregnancy viability and the likelihood of continued normal growth. A poor or weak choriodecidual reaction of the surrounding sac rim, irregular sac contour, and low-set position of the sac within the lower uterine segment are all strong indicators of a nonviable pregnancy, and serial ultrasound follow-up examination is warranted. The first structure to be identified inside the GS, before visualization of the embryo or its cardiac pulsation, is the yolk sac. The next structure to become visible inside the chorionic sac, after the yolk sac, is the early embryo. Once an empty sac or embryonic demise is definitively diagnosed, the spontaneous completion rates with expectant management for such pregnancies are relatively low at around 50-60%.