Table 1. Comparison between the Robson and the modified classification scheme.

Group label	Robson Classification group No.	Characteristics of the group
NS	1	Nulliparous women with a single vertex pregnancy, at ≥37 weeks gestation in spontaneous labor
NI	2a	Nulliparous women with a single vertex pregnancy, at ≥37 weeks gestation who had labor induced
NC	2b	Nulliparous women with a single vertex pregnancy, at ≥37 weeks gestation, who had caesarean section before labor
MS	3	Multiparous women, without a uterine scar, with a single vertex pregnancy at ≥37 weeks gestation in spontaneous labor
MI	4a	Multiparous women, without a uterine scar, with a single vertex pregnancy at ≥37 weeks gestation, who had labor induced
MC	4b	Multiparous women, without a uterine scar, with a single vertex pregnancy at ≥37 weeks gestation, who had caesarean section before labor
PC	5	Multiparous women, with at least one previous caesarean section with a single vertex pregnancy at ≥37 weeks gestation
BR	6+7+9	All women with a single breech, transverse or other abnormal fetal presentation, including women with a uterine scar
TW	8	All women with multiple pregnancies (e.g., twins), including women with a uterine scar
PT	10	All women with a single vertex pregnancy at ≤36 weeks gestation (i.e., preterm), including women with a uterine scar
UK		All women who cannot be classified due to unknown characteristics