Modified classification and composition of caesarean delivery in the Consortium on Safe Labor of the USA, 2002–2008*
| Modified classification group labels (original group labels)† | Characteristics of the group | Proportion of all deliveries (%) | Caesarean rate (%) | Rate of intrapartum caesarean delivery (%) | Proportion of total caesarean (%) |
| NS (1) | Nulliparous women with a single cephalic pregnancy, at ≥37 weeks gestation in spontaneous labour | 16.3 | 14.8 | 14.8 | 7.7 |
| NI (2a) | Nulliparous women with a single cephalic pregnancy, at ≥37 weeks gestation who had labour induced | 15.0 | 31.6 | 31.6 | 15.3 |
| NC (2b) | Nulliparous women with a single cephalic pregnancy, at ≥37 weeks gestation, who had caesarean delivery before labour | 1.6 | 100.0 | 0.0 | 5.0 |
| MS (3) | Multiparous women, without previous caesarean delivery, with a single cephalic pregnancy at ≥37 weeks gestation in spontaneous labour | 20.5 | 3.1 | 3.1 | 2.1 |
| MI (4a) | Multiparous women, without previous caesarean delivery, with a single cephalic pregnancy at ≥37 weeks gestation, who had labour induced | 15.3 | 6.7 | 6.7 | 3.3 |
| MC (4b) | Multiparous women, without previous caesarean delivery, with a single cephalic pregnancy at ≥37 weeks gestation, who had caesarean delivery before labour | 1.0 | 100.0 | 0.0 | 3.1 |
| PC (5) | Multiparous women, with at least one previous caesarean delivery with a single cephalic pregnancy at ≥37 weeks gestation | 11.2 | 82.0 | 11.8 | 29.5 |
| BR (6+7+9) | All women with a single breech, transverse or other abnormal fetal presentation, including women with previous caesarean delivery | 4.8 | 92.6 | 19.0 | 14.3 |
| TW (8) | All women with multiple pregnancies (eg, twins), including women with previous caesarean delivery | 3.4 | 66.6 | 15.2 | 7.3 |
| PT (10) | All women with a single cephalic pregnancy at ≤36 weeks gestation (ie, preterm), including women with previous caesarean delivery | 10.9 | 35.6 | 14.3 | 12.4 |
| Total | 100.0 | 31.2 | 13.1 | 100.0 |
*See text for details on multiple imputation performed.
†The new labelling system corresponds well with the previous numbering system as follows: 1=NS (nulliparous, spontaneous); 2a=NI (nulliparous, induced); 2b=NC (nulliparous, caesarean); 3=MS (multiparous, spontaneous); 4a=MI (multiparous, induced); 4b=MC (multiparous, caesarean); 5=PC (previous caesarean); 6, 7, 9 combined=BR (breech and other non-cephalic presentation); 8=TW (twin and other multiple pregnancies); 10=PT (preterm).