Failed Intrauterine Pregnancy: What Is a Failed Pregnancy, What Is Not?

Pregnancy failure is defined as a lack of sonographic evidence of current or expected viability. Technologic advances in ultrasound imaging continue to redefine diagnostic criteria of pregnancy failure or success. When evaluating a pregnancy, the first step is an assessment of maternal risk factors for failure. Imaging clues such as an empty gestational sac measuring ≥25 mm or an embryo ≥7 mm without cardiac activity are reliable signs of pregnancy failure, whereas embryonic growth <1 mm/d is not. Combinations of sonographic findings can be used for a more accurate prediction of pregnancy success or failure.