OP05.09: “Pseudogestational sac” of ectopic pregnancy: an outmoded and potentially dangerous term

To determine the incidence of intrauterine fluid in patients with ectopic pregnancies, and define the characteristics that distinguish such fluid from an early intrauterine gestational sac. We identified all patients scanned between July 2008 and August 2011, who then proved to have an ectopic pregnancy based on surgery or adnexal sonographic findings. We reviewed the scans to characterize any fluid in the uterus as to shape, contents, and location. Fluid was classified as: type A if it was pointy edged, contained echoes, and/or was located clearly within the uterine cavity; or type B if it was smooth-walled, anechoic, and located in the decidua (as opposed to the uterine cavity). The appearance of type A fluid is inconsistent with a gestational sac, while the appearance of type B overlaps that of a gestational sac. Our study population consisted of 229 women with ectopic pregnancy. In 38 (16.6%), ultrasound demonstrated fluid in the uterus. In 31 of the 38 cases, the fluid was classified as type A. The remaining 7 (3% of 229 ectopics) were classified as type B, only two of whom had no adnexal mass. Based on these results and the incidence of ectopic pregnancy (2% of all pregnancies), we calculated that the probability of ectopic pregnancy is 0.02% in a patient with a positive pregnancy test, an intradecidual smooth-walled anechoic cystic structure, and no adnexal mass, while the probability of intrauterine pregnancy is 99.98%. Fluid in the uterus with ectopic pregnancy can be distinguished from a gestational sac based on shape, fluid contents, and/or location in over 80% of cases. In the remaining cases, the fluid in the uterus appears indistinguishable from, and is highly likely to represent, an early intrauterine gestation. The term “pseudogestational sac” does not apply and its use can potentially lead to interventions that would damage an early intrauterine pregnancy.