Low-resistance endometrial arterial flow in the exclusion of ectopic pregnancy revisited

The objective of this study was to evaluate the efficacy of endometrial arterial flow in the exclusion of ectopic pregnancy. From October 1997 to June 1999, 66 women with elevated beta-human chorionic gonadotropin titers and clinical indications of ectopic pregnancy were evaluated by endovaginal sonography. Women with a gestational sac containing an embryo, a yolk sac, or both were excluded from the study. Doppler ultrasonography was performed in the remaining cases when a definite intrauterine pregnancy could not be visualized. In all cases the thermal index was kept to less than 1.0, consistent with as-low-as-reasonably-achievable principles. Trophoblastic flow was defined as a resistive index of less than 0.6 within the endometrium. Statistical analysis was performed using a 2-tailed t test. Twenty women had ectopic pregnancies; 33 had spontaneous pregnancy losses; and 13 had normal intrauterine pregnancies. A total of 29 women had endometrial trophoblastic flow: 11 of 13 with intrauterine pregnancies, 1 of 20 with ectopic pregnancies, and 17 of 33 with spontaneous pregnancy losses. The negative predictive value for the presence of endometrial low-resistance flow for excluding ectopic pregnancy was 97%. The presence of low-resistance arterial endometrial flow can be a useful sign in diagnosing an early intrauterine pregnancy and decreasing the probability that an ectopic pregnancy is present, particularly in patients with otherwise normal ultrasonographic findings.