Background
The optimal dose of misoprostol to be used in the medical management of miscarriage before 13 weeks has not been resolved.

Aim
To evaluate the effectiveness and side effect profile of two different dosages of misoprostol.

Methods
A randomised controlled, equivalence study comparing 400 vs 800 μg misoprostol per vaginum (PV) on an outpatient basis. The allocated dose was repeated the next day if clinically the products of conception had not been passed. Complete miscarriage was evaluated using two methods: ultrasound criteria on Day 7 and the need for surgical management (clinical criteria). Equivalence was demonstrated if the 95% confidence interval [CI] of the observed risk difference between the two doses for complete miscarriage lay between −15.0 and 15.0%. Differences in side effects and patient satisfaction were evaluated using patient‐completed questionnaires.

Results
One hundred and fifty‐eight women were allocated to receive 400 μg and 152 women to 800 μg misoprostol for the management of missed (91.3%) or incomplete (8.7%) miscarriage. The rate of induced complete miscarriage was equivalent using both ultrasound criteria (observed risk difference (ORD) −4.6%, 95% CI −12.8 to 3.7%; P = 0.313) and clinical criteria (ORD −5.6%, 95% CI −14.8 to 3.6%; P = 0.273). Following the 400 μg dose, the reported rate of fever/rigors was lower (ORD −15.6%, 95% CI −28.1 to −3.0%; P = 0.015), and more women reported their decision to undergo medical management as a good decision (ORD 15.2%, 95% CI 2.8 to 27.7%; P = 0.018).

Conclusion
Four hundred‐microgram misoprostol PV can be recommended for the medical management of miscarriage on an outpatient basis.