We introduced a single-window low-sensitivity urine pregnancy test (LSPT) to replace a double-window LSPT (both 1000 IU hCG) for self-assessment of the outcome of early medical abortion (EMA) (≤63 days gestation) 2 weeks later. We wished to compare assessment of outcomes of EMA with each LSPT. Methods A retrospective review of the outcomes of EMA during 10 months' use of the doublewindow LSPT and the subsequent 10 months' use of the single-window LSPT to compare (i) detection of ongoing

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... ies and (ii) falsepositive and invalid results with each LSPT. Results 492 and 555 women self-assessed the outcome of their EMA with the double-and single-window LSPTs, respectively. Ongoing pregnancies were uncommon and occurred in 4/1047 women (0.4%). Two of these four women did not conduct a LSPT as they presented before the LSPT was due with scant bleeding or continuing pregnancy symptoms. False-positive LSPT results occurred in 6 (1.2%) and 19 (3.4%) double-and single-window LSPT tests, respectively (P=0.0244). Invalid results were reported in 18 (3.6%) and 6 (1.1%) of doubleand single-window LSPT groups, respectively (P=0.01). Conclusion The introduction of the singlewindow LSPT has not impacted on the detection of ongoing pregnancy or on contact with the service due to a positive or invalid LSPT. Services could consider use of either LSPT but should also place emphasis on informing women about the clinical signs and symptoms that suggest failed abortion.