Abstract
With the use of ultrasound examination during the first trimester of pregnancy becoming more widespread, the diagnosis of twin gestations is being made more frequently and earlier in the pregnancy. Similarly, the diagnosis of the first trimester demise of one fetus is also being made earlier and with greater frequency. This phenomenon is referred to as the "vanishing twin."1 The usual complication associated with the disappearing embryo is vaginal bleeding. Serial sonographic examinations of a pregnancy involving this phenomenon will show a distortion of one gestational sac in early pregnancy and disruption of the organization of the embryo, with a decrease in the echogenicity and definition of embryo shape. Over time, sonographic examination will show a separate, fluid-filled space adjacent to the normally progressing pregnancy and, finally, no evidence of the previous gestation.12 We report a case where a vanishing twin was diagnosed at a gestational age of 8 weeks, but upon serial scanning was noted to be an acardiac twin.