Ultrasound of the empty gestation sac in threatened abortion.

The major concern when an empty gestation sac is encountered during threatened abortion is whether or not the pregnancy is viable. Viable pregnancies are managed expectantly, whereas non-viable pregnancies are treated by evacuation of the uterus. Early evacuation of the non-viable pregnancy spares the patient considerable anxiety and discomfort. This study shows that a single ultrasound examination is useful in differentiating viable from non-viable empty gestation sacs. The size of the empty gestation sac was found to be the most useful criterion for determining non-viability. Empty gestation sacs with sizes greater than 26 mm were non-viable, a specificity of 100%, accounting for 43% (42 out of 102) of patients in our series. Other ultrasound criteria found to be useful were shape, position, wall and decidual reaction. The positive predictive value for a successful outcome to a pregnancy was low, being only 41% (9 out of 22).