STUDY QUESTION: What is the efficacy of maintaining or restoring non-pregnant status with low-dose mifepristone combined with misoprostol administered before expected menstruation? SUMMARY ANSWER: Low-dose mifepristone and misoprostol administered at the time of expected menstruation was effective and safe in maintaining or restoring non-pregnant status, with no obvious menstrual disturbance. WHAT IS KNOWN ALREADY: Menstrual regulation involves the medical or mechanical stimulation of uterine sloughing in women with up to 2-3 weeks of menstrual delay. Low-dose mifepristone plus misoprostol is efficacious for termination of ultra-early pregnancy (<= 35 days of amenorrhoea) with no obvious menstrual disturbance. STUDY DESIGN, SIZE, DURATION: A total of 678 women fulfilled all criteria and were recruited. Seventeen women dropped out after deciding to remain pregnant and 11 others were lost to follow-up. Thus, data from 650 women who completed the procedure were included in analyses. Participants were enrolled at any time during their menstrual cycle and administered medication 1 day before expected menstruation. The end of the study was defined on a per-patient basis as the date of completion of the post-treatment menstrual cycle. The primary outcome was the efficacy of abortion induction (for pregnant women) or menstrual regulation (for non-pregnant women). PARTICIPANTS, SETTING, METHODS: Women with regular menstrual cycles (25-35 days) were voluntarily recruited for this study between February 2012 and December 2014. Serum beta-hCG was measured before mifepristone intake. Mifepristone (50 mg) was administered orally 1 day before expected menstruation and 200 mu g misoprostol was administered orally on the day of expected menstruation. Efficacy, disturbance in bleeding patterns in the treatment and post-treatment cycles, satisfaction with the treatment, and subsequent contraception preference were analysed. MAIN RESULTS AND THE ROLE OF CHANCE: Retrospective analysis of serum beta-hCG levels at admission indicated that 23.3% (158/678) of the women were pregnant. The success rate for pregnancy termination was 98.6% (136/138). Two women (1.5%, 2/138) had ongoing pregnancy that was subsequently terminated surgically. The overall bleeding induction rate within 7 days was 98.3% (639/650), with 100% (138/138) in pregnant participants and 97.9% (501/512) in non-pregnant participants. Most pregnant and non-pregnant participants experienced no significant menstrual disturbance during the treatment [96.3% (131/136) versus 97.6% (489/501)] or post-treatment [97.8% (133/136) versus 98.4% (493/501)] menstrual cycle. The general rate of satisfaction with the treatment was 96.7% (618/639). Generally, 36.0% (230/639) of participants preferred to use the regimen as a routine contraception method versus the 64.0% (409/639) who preferred to use it as a remedy for pregnancy prevention after unprotected sex (P < 0.001). LIMITATIONS, REASONS FOR CAUTION: Study participants were recruited from a single region; further studies should include participants from multiple centres in different cities and nations. Given the uncertain efficacy of regimen reuse, the assessment of efficacy was based solely on the first treatment administration. Studies with larger samples and long-term follow-up may provide more data on whether repeated use of this regimen hampers its efficacy. WIDER IMPLICATIONS OF THE FINDINGS: Menstrual regulation with low-dose mifepristone and misoprostol at expected menstruation can be efficacious and highly acceptable to maintain or restore non-pregnant status, which may have potential for routine contraception.