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  1. Discriminatory zone: β-hCG value above which evidence of an intrauterine pregnancy should be seen on transvaginal sonography.

  2. Doubling time: Expected time interval when the β-hCG level doubles in a normal early intrauterine pregnancy. The expected normal increase of hCG is greater than or equal to 50% in 48 hours.

  3. Pregnancy of "unknown location": pregnancy whose location (intra- or extrauterine) cannot be determined sonographically.

Recent improvements in the sonographic depiction of uterine and adnexal structures with transvaginal sonography and refinements in the assay for human chorionic gonadotropin (hCG) have markedly enhanced the sonologist's ability to define the location of early pregnancy. Although the sonographic findings in ectopic pregnancy can be subtle, a definitive diagnosis of this entity is possible in most cases when sonographic findings are combined with results of a single hCG assay or with serial hCG assays. Most importantly, sonography is useful in the evaluation of patients with suspected ectopic pregnancy both to verify the presence or absence of an intrauterine pregnancy, as well as to identify an adnexal ectopic pregnancy. Earlier diagnosis often results in less invasive treatment options and avoidance of rupture, which is a surgical emergency.

Early and confident diagnosis is vital in optimizing the outcome of women with an ectopic pregnancy. Furthermore, sonography plays a vital role in distinguishing women with an ectopic pregnancy that can be treated medically versus those requiring surgical intervention. Also, the possibility that a fallopian tube containing an ectopic pregnancy can be "salvaged" by linear salpingostomy as opposed to partial or complete salpingectomy is closely related to the stage at which the ectopic pregnancy is detected. Once the tube has ruptured, it usually cannot be salvaged. Therefore, it is most desirable to diagnose an ectopic pregnancy as early as possible.

If left unrecognized, an ectopic pregnancy can result in significant maternal morbidity and mortality. Ectopic pregnancy is responsible for 4% to 10% of all maternal deaths.1,2 Even though the diagnosis of ectopic pregnancy is often considered in women who present with lower abdominal pain and amenorrhea, it is missed by the initial examining physician in up to 70% of cases.3 Expeditious and accurate diagnosis of patients who are suspected of having ectopic pregnancy is important so that timely intervention and proper management can be instituted. If it is recognized early, before tubal rupture, it may be possible to surgically remove the gestational sac by linear salpingostomy, thereby preserving the tube and future chances of achieving pregnancy. Advanced ectopic pregnancies can result in significant damage to tubal architecture, which often leads to salpingectomy. If the remaining tube is compromised, fertility can be significantly decreased as a result. Once a patient has had an ectopic pregnancy, there is a significant chance (about 1 in 4) of recurrence in a future pregnancy.3

Early diagnosis is also important for patients undergoing medical treatment of ectopic pregnancy. The success ...

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