To evaluate the reliability of a four-level triage scale for obstetrics and gynaecology emergencies and to explore the factors associated with an optimal triage. Thirty clinical vignettes presenting the most frequent indications for obstetrics and gynaecology emergency consultations were evaluated twice using a computerised simulator. The study was performed at the emergency unit of obstetrics and gynaecology at the Geneva University Hospitals. The vignettes were submitted to nurses and midwives. We assessed inter- and intra-rater reliability and agreement using a two-way mixed-effects intra-class correlation (ICC). We also performed a generalised linear mixed model to evaluate factors associated triage correctness. Triage acuity. We obtained a total of 1191 evaluations. Inter-rater reliability was good (ICC 0.748; 95% CI 0.633-0.858) and intra-rater reliability was almost perfect (ICC 0.812; 95% CI 0.726-0.889). We observed a wide variability: the mean number of questions varied from 6.9 to 18.9 across individuals and from 8.4 to 16.9 across vignettes. Triage acuity was underestimated in 12.4% of cases and overestimated in 9.3%. Undertriage occurred less frequently for gynaecology compared with obstetric vignettes [odds ratio (OR) 0.45; 95% CI 0.23-0.91; P = 0.035] and decreased with the number of questions asked (OR 0.94; 95% CI 0.88-0.99; P = 0.047). Certification in obstetrics and gynaecology emergencies was an independent factor for the avoidance of undertriage (OR 0.35; 95% CI 0.17-0.70; P = 0.003). The four-level triage scale is a valid and reliable tool for the integrated emergency management of obstetrics and gynaecology patients. The Swiss Emergency Triage Scale is a valid and reliable tool for obstetrics and gynaecology emergency triage.