Table 3.
Assessment of the type of population
| Steps for interpretation | Interpretation by Robson | Example: MCS population | Our findings | Additional information from the database used to interpret data | Final interpretation |
| STEP 1. Size of group 1+group 2 | 35%–42% | 38.1% | 38.1% | – | Rate in line with both references by Robson and the MCS reference population. |
| STEP 2. Size of groups 3+4 | 30% | 46.5% | 37.3% | Multiparous in our population 55.0% | Rate higher than Robson references but lower than MCS examples. This may be explained by a high prevalence of multiparous women in our population. |
| STEP 3. Size of group 5 | Half of total CS rate | 7.2% | 10.9% | – | Lower than half of total CS. This, as suggested by the WHO manual, may be due to relatively low CS rate in the previous years, or to a recently increased CS rate or to misclassification. |
| STEP 4. Size of groups 6+7 | 3%–4% | 2.7% | 3.4% | – | Rate in line with both Robson references and MCS examples. |
| STEP 5. Size of group 8 | 1.5%–2% | 0.9% | 1.1% | – | Rate in line with MCS examples. |
| STEP 6. Size of group 10 | <5% | 4.2% | 7.8% | Divisions by gestational age in our preterm population | Higher than both comparisons. This may be explained by the hospital being a tertiary care referral centre, or by misclassification. |
| STEP 7. Ratio of the size of group one versus group 2 | Ratio 2 or higher | Ratio 3.3 | Ratio 1.5 | Indication of IOL | Lower than the comparisons. This associates with a large size of group 2a, suggesting a high incidence of IOL. This may be explained by: (1) Case selection (tertiary care referral centre). (2) Inappropriate indication to IOL (deserving further investigation). |
| STEP 8. Ratio of size of group 3 versus group 4 | > 2:1 | Ratio 6.3 | Ratio 2.6 | Indication of IOL | Rate in line with both Robson references, lower than MCS. This may be explained by: (1) Misclassification of augmentation as IOL. (2) Case selection (tertiary care referral centre). (3) Inappropriate indication to IOL (deserving further investigation). |
| STEP 9. Ratio of size of group 6 versus group 7 | Usually 2:1 | Ratio 0.8 | Ratio 1.2 | Multiparous in our population 55.0% | Rate in line with MCS, but lower than Robson references. This may be explained by: (1) High number of multiparous women in our population. |
CS, caesarean section; IOL, induction of labour; MCS, Multicountry Survey; MCS reference population: was the population of the WHO MCS with relatively low CS rates and, at the same time, with good outcomes of labour and childbirth.