OBJECTIVE To evaluate the performance of a one-step test detecting intact hCG and free β-hCG isoforms in the urine of pregnant women to diagnose an abnormal pregnancy. DESIGN Prospective study. SETTING Emergency gynecology departments in teaching hospitals. PATIENT(S) Five hundred twenty-six patients were enrolled, 272 who were not pregnant and 254 who were pregnant. INTERVENTION(S) AND MAIN OUTCOME MEASURE(S) Semiquantitative determination of intact urinary hCG of supposedly not pregnant and pregnant women with vaginal bleeding and/or vaginal pain between 5 and 8 weeks of amenorrhea. RESULT(S) The sensitivity and specificity of the urine test for diagnosing nonpregnancy were, respectively, 100% (252/252) and 100% (272/272). The sensitivity and specificity of the urine test for diagnosing ectopic pregnancy (EP) were, respectively, 97% (32/33) and 83% (142/171). The negative predictive value is 99.3% (142/143). The sensitivity and specificity or the urine test for diagnosing miscarriage were, respectively, 89.6% (43/48) and 83% (142/171). The negative predictive value is 96.6% (142/147). CONCLUSION(S) Abnormal pregnancy, such as an EP or a miscarriage, can be rapidly detected with the one-step test for intact hCG and free β-hCG isoforms. If ultrasound cannot confirm the localization and/or evolution of a pregnancy, using this test reduces medical supervision and repeated quantification of hCG.