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Robson's viewpoint on the issue of a caesarean section rate (1) is that we should be concerned, not at what the caesarean section rate SHOULD be but at what the true section rate is now and why? We are unable to compare rates around the country or even nationally if we are not comparing like with like. Hence the need for a classification system. This way we can analyse what is currently the trend with the impetus to improve perinatal care. This may not result in a reduction in the section rate or even aim to do so. Who knows what the ideal section rate should be?

For a classification system to be useful, it needs to fill some simple criteria. Simply put, it needs to be easy to understand and to then implement. Each group in the system has to be mutually EXCLUSIVE whilst totally INCLUSIVE. In other words, there needs to be a group available into which you can classify the type of section but only one group that is truly applicable to each case.

The 10 group classification system is based on 4 main areas: the category of pregnancy, the woman's previous obstetric record, whilst accounting for the type of labour and delivery as well as the gestation of the pregnancy. Robson reiterates how important it is that the system is robust and well thought out from the beginning, as it is important that it is not being constantly changed. He is not trying to suggest that the 10 groups are finite but suggests that the groups themselves may need further analysis in order to be thorough. Only by auditing current practice can we hope to improve it.

The categories are as follows:

1. Nulliparous women with a single cephalic pregnancy, at greater than or equal to 37 weeks gestation in spontaneous labour
2. Nulliparous women with a single cephalic pregnancy, at greater than or equal to 37 weeks gestation who either had labour induced or were delivered by a caesarean section before labour
3. Multiparous women, without a previous uterine scar, with a single cephalic pregnancy at greater than or equal to 37 weeks in spontaneous labour
4. Multiparous women, without a previous uterine scar, with a single cephalic pregnancy at greater than or equal to 37 weeks who either had labour induced or were delivered by a caesarean section
5. All multiparous women, with at least one previous uterine scar and a single cephalic pregnancy at greater than or equal to 37 weeks gestation
6. All nulliparous women with a single breech pregnancy
7. All multiparous women with a single breech pregnancy including, women with previous uterine scars
8. All women with multiple pregnancies, including women with previous uterine scars
9. All women with a single pregnancy with a transverse or oblique lie, including women with previous uterine scars
10. All women with a single cephalic pregnancy at less than or equal to 36 weeks gestation, including women with previous scars.

Each group accounts for a particular type of population. The first group is traditionally a low risk population but in itself is a large proportion of pregnant women and therefore accounts for a sizable percentage of the section rate. Group 3 is a very consistent group. In fact, it is so consistent that Robson comments it is a useful indicator of how accurate the data collection has been.

References

1. Robson MS. Classification of Caesarean Sections. Fetal and Maternal Medicine Review 2001;12(1):23-39