Robson Classification System Applied to Induction of Labor

Induction of labor (IL) is a common obstetric procedure, but it is questionable whether or not it results in higher cesarean section (CS) rates. The present study aims to evaluate the impact of IL in the overall CS rates and to analyze these rates according to the method of IL employed and to the Robson group in which it was applied.

Methods

We have conducted a retrospective study including pregnant women whose labor was induced at a tertiary hospital in 2015 and 2016. All women were classified according to the Robson Classification System (RCS). The CS rates were analyzed and compared regarding the method of IL employed.

Results

A total of 1,166 cases were included. The CS rate after IL was 20.9%, which represented 23.1% of the total of CSs performed in 2015 and 2016. The highest CS rates were recorded in RCS groups 5 (65.2%) and 8 (32.3%). Group 2 was the highest contributor to the overall CS rate, since it represented 56.7% of the population. The intravaginal prostaglandins method was the most used (77%). Transcervical Foley catheter was the preferredmethod in group 5 and intravaginal prostaglandins in all the other groups. The CS rate was higher when transcervical Foley catheter was used (34.1%).

Conclusion

Transcervical Foley catheter induction was associated with a higher rate of CS, probably because it was the preferred method used in group 5.

Keywords:
induction of labor; cesarean section; robson classification

Group	Description
1	Nulliparous, single cephalic, ≥37 weeks, in spontaneous labor
2	Nulliparous, single cephalic, ≥37 weeks, induced or CS before labor
3	Multiparous (excluding previous CS), single cephalic, ≥37 weeks, in spontaneous labor
4	Multiparous (excluding previous CS), single cephalic, ≥37 weeks, induced or CS before labor
5	Previous CS, single cephalic, ≥37 weeks
6	All nulliparous breeches
7	All multiparous breeches
8	All multiple pregnancies (including previous CS)
9	All abnormal lies (including previous CS)
10	All single cephalic, ≤36 weeks (including previous CS)

Groups	CS rate^a % (number of CS in the group/number of women in the group);	Relative size of the group^b % (number of women in the group/total number of IL);	Absolute contribution to the overall CS rate^c % (number of CS in the group/ total number of IL);	Relative contribution to the overall CS rate^d % (number of CS in the group /total number of CS).
Group 2	22.4 (148/661)	56.7 (661/1,166)	12.7 (148/1,166)	60.7 (148/244)
Group 4	8.3 (27/326)	28 (326/1,166)	2.3 (27/1,166)	11.1 (27/244)
Group 5	65.2 (43/66)	5.7 (66/1,166)	3.7 (43/1,166)	17.6 (43/244)
Group 6	0 (0/4)	0.3 (4/1,166)	0 (0/1,166)	0 (0/244)
Group 7	20 (1/5)	0.4 (5/1,166)	0.1 (1/1,166)	0.4 (1/244)
Group 8	32.3 (10/31)	2.7 (31/1,166)	0.9 (10/1,166)	4.1 (10/244)
Group 10	20.6 (15/73)	6.3 (73/1,166)	1.3 (15/1,166)	6.2 (15/244)
Total	–	100 (1,166/1,166)	20.9 (244/1,166)	100 (244/244)

Groups	Transcervical Foley catheter		Intravenous oxytocin		Intravaginal prostaglandins
Groups	IL^a % (number of IL in the group with each method/total number of women in the group);	CS rate^b % (number of CS in the group with each method/number of IL in the group with each method).	IL^a % (number of IL in the group with each method/total number of women in the group);	CS rate^b % (number of CS in the group with each method/number of IL in the group with each method).	IL^a % (number of IL in the group with each method/total number of women in the group);	CS rate^b % (number of CS in the group with each method/number of IL in the group with each method).
Group 2	15.6 (103/661)	22.3 (23/103)	4.8 (32/661)	6.3 (2/32)	79.6 (526/661)	23.4 (123/526)
Group 4	7.1 (23/326)	21.7 (5/23)	8.6 (28/326)	7.1 (2/28)	84.4 (275/326)	7.3 (20/275)
Group 5	74.2 (49/66)	67.4 (33/49)	22.7 (15/66)	66.7 (10/15)	3 (2/66)	0 (0/2)
Group 6	0 (0/4)	0 (0/0)	0 (0/4)	0 (0/0)	100 (4/4)	0 (0/4)
Group 7	0 (0/5)	0 (0/0)	0 (0/5)	0 (0/0)	100 (5/5)	20 (1/5)
Group 8	3.2 (1/31)	100 (1/1)	9.7 (3/31)	66.7 (2/3)	87.1 (27/31)	25.9 (7/27)
Group 10	12.3 (9/73)	11.1 (1/9)	6.9 (5/73)	40 (2/5)	80.8 (59/73)	20.3 (12/59)
Total	15.9 (185/1,166)	34.1 (63/185)	7.1 (83/1,166)	21.7 (18/83)	77 (898/1166)	18.2 (163/898)

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[1] Address for correspondence
Sara Vargas, MD, Centro Hospitalar de Lisboa Norte, Avenida Professor Egas Moniz, 1649-035, Lisboa, Portugal (e-mail: saravargasp@gmail.com).