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Analysis of cesarean section rates in two German hospitals applying the 10-Group Classification System

  • Christina Pulvermacher , Patricia Van de Vondel , Lydia Gerzen , Ulrich Gembruch , Thomas Welchowski , Matthias Schmid and Waltraut M. Merz
Published/Copyright: April 8, 2021
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Journal of Perinatal Medicine
From the journal Journal of Perinatal Medicine Volume 49 Issue 7

Abstract

Objectives

In Germany, cesarean section (CS) rates more than doubled within the past two decades. For analysis, auditing and inter-hospital comparison, the 10-Group Classification System (TGCS) is recommended. We used the TGCS to analyze CS rates in two German hospitals of different levels of care.

Methods

From October 2017 to September 2018, data were prospectively collected. Unit A is a level three university hospital, unit B a level one district hospital. The German birth registry was used for comparison with national data. We performed two-sample Z tests and bootstrapping to compare aggregated (unit A + B) with national data and unit A with unit B.

Results

In both datasets (national data and aggregated data unit A + B), Robson group (RG) 5 was the largest contributor to the overall CS rate. Compared to national data, group sizes in RG 1 and 3 were significantly smaller in the units under investigation, RG 8 and 10 significantly larger. Total CS rates between the two units differed (40.7 vs. 28.4%, p<0.001). The CS rate in RG 5 and RG 10 was different (p<0.01 for both). The most relative frequent RG in both units consisted of group 5, followed by group 10 and 2a.

Conclusions

The analysis allowed us to explain different CS rates with differences in the study population and with differences in the clinical practice. These results serve as a starting point for audits, inter-hospital comparisons and for interventions aiming to reduce CS rates.

Keywords: 10-Group Classification System; audit; cesarean section rates; cesarean section statistics; cesarean section trends; delivery; health care; quality indicators; Robson classification; TGCS

Introduction

In Germany, the cesarean section (CS) rate more than doubled within two decades (from 15.3% in 1991 to 32.2% in 2011) [1]. This trend is reflecting the global development [2], [3]. According to latest figures on the world’s births, 21.1% of all babies (95% uncertainty interval 19.1–22.4) are born by CS [3]. Inequalities in CS rates are present between world regions, with underuse e.g. in West Africa (4.1% CS rate, 95% uncertainty interval 3.6–4.6) and overuse, e.g. in Latin America (44.3%, 95% uncertainty interval 41.2–47.4) [3]. Even within one country, CS rates diverge. For example, in the 16 federal German states CS rates in 2017 ranged between 24.0 and 37.2% [4]. Causes for over- and underuse of CS are widely debated, and the ideal CS rate is a topic of much controversy [5], [6], [7], [8], [9]. Factors affecting the frequency of CS include, among others, women’s and health care providers’ attitudes as well as organizational and system factors [10], [11].

A prerequisite for analysis, auditing, and inter-hospital comparison is a standardized classification system for cesarean sections. The 10-Group Classification System (TGCS) has emerged as the most appropriate classification system [12], [13], [14], [15], [16]. Compared to other classifications which are based on indications for CS or their urgency, the TGCS employs a woman’s obstetric history and findings. The TGCS is totally inclusive and mutually exclusive; it is considered simple, robust, reliable, and flexible [14]. Since its introduction in 2001 [12], numerous reports including longitudinal and cross-sectional studies using the TGCS have been published [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28] including a systematic review reporting the experience with the TGCS in 31 countries and some 33 million pregnancies [29].

So far, German CS data have not been analyzed according to the TGCS. Recently published German guidelines strongly recommend the TGCS use [30]. We applied the TGCS to prospectively collected data from two German hospitals of different levels of care. An inter-hospital comparison was performed; additionally, we compared the data to national figures. The aim of our study was to identify differences between the two units and deviations from the national data; and to identify the Robson groups contributing most to the overall CS rate in the respective unit. We hypothesized that the difference in the overall CS rate between the two units is owed to differences in the population served rather than differences in the clinical practice.

Patients and methods

The study was conducted at two obstetric departments in North-Rhine Westfalia, Germany’s most populous federal state. Obstetric department A (unit A), a level three university hospital, serves as a regional referral center; a high proportion of at-risk pregnancies, including women with preexisting medical conditions and pregnancies with fetal anomalies are attended to. Obstetric department B (unit B), a level one district hospital, serves an urban, predominantly low-risk population.

From October 2017 to September 2018, data of all CS performed at the two study sites were collected and classified according to the TGCS specifications. The study was approved by the Ethics Committee of the Faculty of Medicine, University Bonn (no. 261/17). Women scheduled for elective CS were informed about the study and gave their written consent during the antenatal visit. In case of emergency CS, women were informed about the study before or after the surgery, depending on timing and urgency, and gave their consent at that time.

We defined birth according to the World Health Organization (WHO) as any delivery – live birth or stillbirth – of a fetus with a gestational age ≥22 completed weeks of gestation or a birth weight ≥500 g [16]. We excluded births after termination of pregnancy, if gestational age was <22 completed weeks or birth weight was <500 g, corresponding to 3.2% (66/2047) of all deliveries in unit A during the study period (0.13%, 2/1,599 in unit B, respectively). All cases were classified according to the TGCS, see Tables 1 –4 [12, 13, 16].

Table 1:

TGCS report table unit A. Study period: October 1, 2017 to September 30, 2018.

Column 1 Column 2 Column 3 Column 4 Column 5 Column 6 Column 7
Robson group Total number of CS in each group, n Total number of women delivered in each group, n Group size % (n of women in the group/total n women delivered in the hospital × 100) Group CS rate % (n of CS in the group/total n of women in the group × 100) Absolute group contribution to overall CS rate % (n of CS in the group/total n of women delivered in the hospital × 100) Relative group contribution to overall CS rate % (n of CS in the group/total n of CS in the hospital × 100)
1 Nulliparous, single cephalic, ≥37 weeks, in spontaneous labor 48 367 17.9 13.1 2.3 5.8
2 Nulliparous, single cephalic, ≥37 weeks, induced or CS before labor 178 343 16.8 51.9 8.7 21.3
2a Nulliparous, single cephalic, ≥37 weeks, induced 103 268 13.1 38.4 5.0 12.4
2b Nulliparous, single cephalic, ≥37 weeks, CS before labor 75 75 3.7 100 3.7 9.0
3 Multiparous (excl. prev CS), single cephalic, ≥37 weeks, in spontaneous labor 9 396 19.4 2.3 0.4 1.1
4 Multiparous, single cephalic, ≥37 weeks, induced or CS before labor 30 193 9.4 15.5 1.5 3.6
4a Multiparous (excl. prev CS), single cephalic, ≥37 weeks, induced 10 173 8.5 5.8 0.5 1.2
4b Multiparous (excl. prev CS), single cephalic, ≥37 weeks, CS before labor 20 20 1.0 100 1.0 2.4
5 Previous CS, single cephalic, ≥37 weeks 211 260 12.7 81.2 10.3 25.3
6 All nulliparous breeches 65 69 3.4 94.2 3.2 7.8
7 All multiparous breeches (including previous CS) 49 50 2.4 98.0 2.4 5.9
8 All multiple pregnancies (including previous CS) 83 106 5.2 78.3 4.1 10.0
9 All abnormal lies (including previous CS) 13 13 0.6 100 0.6 1.6
10 All single <37 weeks cephalic pregnancies (including prev CS) 148 250 12.2 59.2 7.2 17.7
Total 834 2,047 100 40.7 40.7 100
Table 2:

TGCS report table unit B. Study period: October 1, 2017 to September 30, 2018.

Column 1 Column 2 Column 3 Column 4 Column 5 Column 6 Column 7
Robson group Total number of CS in each group, n Total number of women delivered in each group, n Group size % (n of women in the group/total n women delivered in the hospital × 100) Group CS rate % (n of CS in the group/total n of women in the group × 100) Absolute group contribution to overall CS rate % (n of CS in the group/total n of women delivered in the hospital × 100) Relative group contribution to overall CS rate % (n of CS in the group/total n of CS in the hospital × 100)
1 Nulliparous, single cephalic, ≥37 weeks, in spontaneous labor 43 341 22.0 12.6 2.8 9.8
2 Nulliparous, single cephalic, ≥37 weeks, induced or CS before labor 82 198 12.8 41.1 5.3 18.6
2a Nulliparous, single cephalic, ≥37 weeks, induced 45 161 10.4 28.0 2.9 10.2
2b Nulliparous, single cephalic, ≥37 weeks, CS before labor 37 37 2.4 100 2.4 8.4
3 Multiparous (excl. prev CS), single cephalic, ≥37 weeks, in spontaneous labor 10 393 25.3 2.5 0.6 2.3
4 Multiparous, single cephalic, ≥37 weeks, induced or CS before labor 26 137 8.8 19.0 1.7 5.9
4a Multiparous (excl. prev CS), single cephalic, ≥37 weeks, induced 11 122 7.9 9.0 0.7 2.5
4b Multiparous (excl. prev CS), single cephalic, ≥37 weeks, CS before labor 15 15 1.0 100 1.0 3.4
5 Previous CS, single cephalic, ≥37 weeks 134 201 12.9 66.7 8.6 30.4
6 All nulliparous breeches 42 64 4.1 65.6 2.7 9.5
7 All multiparous breeches (including previous CS) 26 41 2.6 63.4 1.7 5.9
8 All multiple pregnancies (including previous CS) 27 54 3.5 50.0 1.7 6.1
9 All abnormal lies (including previous CS) 6 6 0.4 100 0.4 1.4
10 All single <37 weeks cephalic pregnancies (including prev CS) 45 117 7.5 38.5 2.9 10.2
Total 441 1,552 100 28.4 28.4 100
Table 3:

TGCS report table Germany. Study period: January 1, 2017 to December 31, 2017 [31].

Column 1 Column 2 Column 3 Column 4 Column 5 Column 6 Column 7
Robson group Total number of CS in each group, n Total number of women delivered in each group, n Group size % (n of women in the group/total n women delivered in the hospital × 100) Group CS rate % (n of CS in the group/total n of women in the group × 100) Absolute group contribution to overall CS rate % (n of CS in the group/total n of women delivered in the hospital × 100) Relative group contribution to overall CS rate % (n of CS in the group/total n of CS in the hospital × 100)
1 Nulliparous, single cephalic, ≥37 weeks, in spontaneous labor 36,505 202,418 26.6 18.0 4.8 15.4
2 Nulliparous, single cephalic, ≥37 weeks, induced or CS before labor 45,740 103,547 13.6 44.2 6.0 19.4
3 Multiparous (excl. prev CS), single cephalic, ≥37 weeks, in spontaneous labor 7,503 193,282 25.4 3.9 1.0 3.2
4 Multiparous, single cephalic, ≥37 weeks, induced or CS before labor 13,396 64,650 8.5 20.7 1.8 5.7
5 Previous CS, single cephalic, ≥37 weeks 71,201 103,154 13.6 69.0 9.4 30.1
6 All nulliparous breeches 19,857 21,382 2.8 92.9 2.6 8.4
7 All multiparous breeches (including previous CS) 10,334 12,112 1.6 85.3 1.4 4.4
8 All multiple pregnancies (including previous CS) 11,058 14,773 1.9 74.9 1.5 4.7
9 All abnormal lies (including previous CS) 2,929 2,929 0.4 100 0.4 1.2
10 All single <37 weeks cephalic pregnancies (including prev CS) 17,873 41,859 5.5 42.7 2.4 7.6
Total 236,396 760,106 100 31.1 31.1 100
Table 4:

TGCS report table Bavaria. Study period: January 1, 2018 to December 31, 2018 [32].

Column 1 Column 2 Column 3 Column 4 Column 5 Column 6 Column 7
Robson group Total number of CS in each group, n Total number of women delivered in each group, n Group size % (n of women in the group/total n women delivered in the hospital × 100) Group CS rate % (n of CS in the group/total n of women in the group × 100) Absolute group contribution to overall CS rate % (n of CS in the group/total n of women delivered in the hospital × 100) Relative group contribution to overall CS rate % (n of CS in the group/total n of CS in the hospital × 100)
1 Nulliparous, single cephalic, ≥37 weeks, in spontaneous labor 5,794 35,753 29.4 16.2 4.8 15.1
2 Nulliparous, single cephalic, ≥37 weeks, induced or CS before labor 8,214 19,416 16.0 42.3 6.8 21.4
2a Nulliparous, single cephalic, ≥37 weeks, induced 4,866 16,068 13.2 30.3 4.0 12.7
2b Nulliparous, single cephalic, ≥37 weeks, CS before labor 3,348 3,348 2.7 100 2.8 8.7
3 Multiparous (excl. prev CS), single cephalic, ≥37 weeks, in spontaneous labor 1,035 23,300 19.2 4.4 0.9 2.7
4 Multiparous, single cephalic, ≥37 weeks, induced or CS before labor 2,130 8,976 7.4 23.7 1.8 5.6
4a Multiparous (excl. prev CS), single cephalic, ≥37 weeks, induced 518 7,364 6.1 7.0 0.4 1.4
4b Multiparous (excl. prev CS), single cephalic, ≥37 weeks, CS before labor 1,612 1,612 1.3 100 1.3 4.2
5 Previous CS, single cephalic, ≥37 weeks 11,265 18,211 15.0 61.9 9.3 29.4
6 All nulliparous breeches 3,628 4,151 3.4 87.4 3.0 9.5
7 All multiparous breeches (including previous CS) 1,620 2,008 1.7 80.7 1.3 4.2
8 All multiple pregnancies (including previous CS) 1,569 2,410 2.0 65.1 1.3 4.1
9 All abnormal lies (including previous CS) 496 496 0.4 100 0.4 1.3
10 All single <37 weeks cephalic pregnancies (including prev CS) 2,611 6,829 5.6 38.2 2.2 6.8
Total 38,362 121,550 100 31.6 31.6 100

For classification of national data, the German birth registry 2017 was utilized [31]. These data did not allow a subdivision of Robson group 2 (nulliparous, single cephalic ≥37 weeks) and 4 (multiparous, single cephalic ≥37 weeks). Therefore, the Bavarian birth registry 2018 was used for the comparison of subgroups 2a (induced) and 2b (CS before labor) (4a and 4b, respectively) [32].

Statistical analysis

The aggregated data tables of the TGCS were established for unit A, unit B, Germany, and Bavaria, see Tables 1 –4. Within each location, the following numbers were calculated:

  1. number of CS in each Robson group (column 2);

  2. number of women delivered in each Robson group (column 3);

  3. number of CS in each Robson group divided by the total number of women delivered in the hospital (column 4);

  4. number of CS in each Robson group divided by the total number of women in this group (column 5);

  5. number of CS in each Robson group divided by the number of women delivered in the hospital for each Robson group (column 6);

  6. number of CS in each Robson group divided by the total number of CS in the hospital (column 7).

For the German national data set the total number of births (CS and vaginal) exceeded the numbers reported in the aggregated table for Germany by 12,048 cases for CS (and 16,082 for vaginal births, respectively). Since these numbers should conform, the excess cases were redistributed among the Robson groups proportional to the relative frequency distributions of CS and women delivered in the hospital. In the Bavarian birth registry, 10,818 excess cases of vaginal deliveries were redistributed in analogy. Additionally, Robson group 2b, 4b and 9 was corrected if the CS rate within those groups did not add to 100%.

After pre-processing of the data we compared the aggregated data of unit A + B vs. Germany for each category and each Robson group separately with two-sample Z test for equality of proportions. The normal approximation was reasonable, because even in the Robson subgroups the sample sizes consisted of several hundred cases. The numbers for Germany were reduced by the number of cases from unit A + B to avoid intersection between those data sets. The p-values were adjusted for multiple comparisons with the Bonferroni-Holm procedure [33] regarding all p-values of the Robson groups within a category. Thereafter, the aggregated data set of unit A + B was compared to the Bavarian figures. Finally, a comparison between unit A and unit B was performed using the same statistical approach.

If CS rates are to be curbed in both units it is advisable to perform interventions in those Robson groups where the largest reduction can be expected. The identification of differences between most probable Robson groups between unit A and unit B supports this decision process. Therefore we estimated nonparametric bootstrap percentile intervals based on the aggregated CS rates of unit A and unit B (100,000 samples were drawn, percentile method) [34]. Here, the statistics of interest in both, CS and non-CS groups of unit A and unit B were if the most, second most and third most relative frequent Robson groups differed between unit A and unit B.

Results

Tables 1 –4 comprise the report tables according to the TGCS of unit A, unit B, Germany, and Bavaria.

Comparison between aggregated data (unit A + B) and national/Bavarian figures

In both datasets (aggregated data unit A + B and national data), Robson group 5 (previous CS, single cephalic, ≥37 weeks of gestation) was the largest contributor to the overall CS rate (relative group contribution aggregated data unit A + B: 27.1%; Germany: 30.1%), even though the group size was only third place (fourth place in Germany, respectively). CS rates in Robson group 5 were similar, with the majority of women (unit A + B: 74.8%, Germany: 71.1%) delivering by elective repeat CS.

Compared to national data, the size of Robson group 1 (nulliparous women with term singleton pregnancy, cephalic presentation, entering labor spontaneously) was significantly smaller in unit A + B (19.7 vs. 26.6%, p<0.001). The CS rate in this Robson group was significantly lower in unit A + B (12.9 vs. 18.6%, p<0.001), resulting in an overall smaller absolute (2.5 vs. 4.9%, p<0.001) and relative (7.1 vs. 15.4%, p<0.001) contribution of this group to the total CS rate.

Likewise, the size of Robson group 3 (multiparous women with term singleton pregnancy, cephalic presentation, entering labor spontaneously) was significantly smaller in unit A + B (21.9 vs. 25.4%, p<0.001) compared to national data. Even though the CS rate in this Robson group did not differ between unit A + B and national data, an overall smaller absolute (0.5 vs. 1.0%, p<0.05) and relative (1.5 vs. 3.2%, p<0.01) contribution of this group to the overall CS rate was present.

On the contrary, compared to national data the size of Robson group 8 (multiple pregnancies) and 10 (preterm deliveries) was significantly higher in unit A + B (Robson group 8: 4.4 vs. 1.9%, p<0.001; Robson group 10: 10.2 vs. 5.5%, p<0.001), resulting in a higher absolute (Robson group 8: 3.1 vs. 1.5%, p<0.001; Robson group 10: 5.4 vs. 2.4%, p<0.001) and relative (Robson group 8: 8.6 vs. 4.7%, p<0.001; Robson group 10: 15.1 vs. 7.6%, p<0.001) contribution of these Robson groups to the total CS rate in unit A + B.

Further differences between the national data and unit A + B pertained to Robson group 6 and 7 (nulliparous and multiparous women with breech presentation). Due to the small size of these Robson groups, the higher number of women (Robson group 6: 3.7 vs. 2.8%, p<0.01; Robson group 7: 2.5 vs. 1.6%, p<0.001) did not translate into a higher relative contribution to the overall CS rate.

No difference was present between aggregated data of unit A + B and national data for Robson group 2 and 4 (nulliparous (multiparous, respectively), single cephalic ≥37 weeks, induced or CS before labor). However, national data did not allow to differentiate between induction of labor (IoL) (Robson group 2a and 4a) and elective CS (Robson group 2b and 4b). The comparison with Bavarian figures revealed a significantly higher group size of multiparous women for IoL (Robson group 4a) in unit A + B (8.2 vs. 6.1%, p<0.001).

Comparison between unit A and unit B

Total CS rates differed by 12.3% between unit A and B, corresponding to a 43.3% higher CS rate in unit A (p<0.001).

Figure 1 depicts the Robson group sizes and relative contributions to the overall CS rate in both units, Figure 2 for subgroups 2a/b and 4a/b (nulliparous (multiparous, respectively), single cephalic ≥37 weeks, induced or CS before labor).

Figure 1: Group size (%) and relative contribution to the overall CS rate (%) of the 10 Robson groups in unit A and unit B.
Figure 1:

Group size (%) and relative contribution to the overall CS rate (%) of the 10 Robson groups in unit A and unit B.

Figure 2: Group size (%) and relative contribution to the overall CS rate (%) of Robson group 2a + b and 4 a + b in unit A and unit B.
Figure 2:

Group size (%) and relative contribution to the overall CS rate (%) of Robson group 2a + b and 4 a + b in unit A and unit B.

Nulliparous women with single cephalic pregnancy ≥37 weeks of gestation (Robson group 1 + 2) comprised the largest group in both units (34.7 and 34.8%, respectively), with a nearly 1:1 ratio between Robson group 1 and 2 in unit A. CS rates in Robson group 1 were similar in both units (13.1 and 12.6%). The CS rate in Robson group 2a (nulliparous, single cephalic, ≥37 weeks, induced) was 38.4% in unit A vs. 28.0% in unit B. The difference in the absolute contribution of this group to the total CS rate was significant (5.0 vs. 2.9%, p<0.01).

In both units, Robson group 5 (previous CS, single, cephalic, ≥37 weeks of gestation) was the largest contributor to the overall CS rate (25.3% in unit A, 30.4% in unit B). Whereas the group size was similar in both units (12.5% in unit A and 12.9% in unit B) the difference in CS rates between unit A and unit B was significant (81.2 vs. 66.7%, p<0.01).

The number of preterm deliveries (Robson group 10) differed by 4.7% (12.2% in unit A vs. 7.5% in unit B), corresponding to a 62.7% higher preterm delivery rate in unit A (p<0.001). The CS rate of this group was higher in unit A (59.2 vs. 38.5%, p<0.01), resulting in a significantly different relative group contribution of this Robson group to the total CS rate (17.7 vs. 10.2%, p<0.01).

Comparison of the most frequent Robson groups between unit A and unit B

The groups with the highest relative CS rates in both units were Robson group 5, 10, and 2a. Relative frequencies in unit A were 25.3, 17.8 and 12.4% for Robson group 5, 10, and 2a (30.4, 10.2, and 10.2% for unit B, respectively).

The nonparametric bootstrap percentile interval of the probability that the most frequent Robson group differed between unit A and B was [0.0004, 0.0006]. The respective intervals for the second and third relative frequent Robson groups were [0.6750, 0.6808] and [0.7684, 0.7737], respectively. Therefore, there is evidence that the most relative frequent Robson group was identical in unit A and unit B, whereas in the majority of cases the second and third most relative frequent Robson group was different.

Performing the same calculation with merged data of Robson groups 1 + 2a + 2b, corresponding to all nulliparous women with single cephalic pregnancy ≥37 weeks of gestation, the order of the highest three relative CS frequencies in unit A changed to 1 + 2a + 2b, 5, and 10 (27.1, 25.3, and 17.8%). For unit B, the sequence of the most frequent Robson groups changed to 5, 1 + 2a + 2b, and 10 (30.4, 28.3, and 10.2%).

In the case of the merged data, the nonparametric bootstrap percentile interval of the probability that the most frequent Robson group differed between unit A and B was [0.6113, 0.6173]. The respective intervals for the second and third relative frequent Robson group were [0.6111, 0.6171] and [0.3592, 0.3651], respectively. Therefore, there is evidence that the highest and second highest relative frequent Robson groups were different in unit A and unit B in most cases, and the Robson group of the third highest relative frequency was not.

Discussion

The application of the TGCS for comparison of CS rates between two German hospitals of different levels of care and national figures revealed consistencies and differences in the respective Robson groups. The analysis allowed us to attribute these variations to the patient population served at the respective unit and to differences in the clinical practice. Furthermore, the results provided clues about the most effective approach for targeting a reduction in the CS rate of each unit.

Comparison between aggregated data (unit A + B) and national/Bavarian figures

In both datasets, Robson group 5 (previous CS, singleton, cephalic, ≥37 weeks of gestation) was the most significant contributor to the overall CS rate. Apart from being a consequence of the group size, this finding illustrates the clinical practice of delivery after previous CS in Germany. Brennan et al. [18] compared data of nine institutions in different countries, comprising 47,402 births. They found a high correlation between the total CS rate and the CS rate in Robson group 1 + 2 (nulliparous women with single cephalic pregnancy ≥37 weeks of gestation) [18]. Colais et al. [19] retrospectively analyzed 64,423 births in the northern region of Italy. Here, the CS rate in Robson group 5 was even higher (93.6%), but the contribution of this Robson group to the overall CS rate is not mentioned [19]. Rossen et al. [25] compiled data of three level 3 hospitals in Norway, Ireland and Slovenia. In all three centers, the size of Robson group 5 was smaller, and the absolute contribution of Robson group 5 to the total CS rate was lower compared to German national data [25]. Pyykönen et al. [24] investigated births in five Nordic countries (Denmark, Finland, Iceland, Norway and Sweden) in a cross-sectional and longitudinal design. The increase in the overall CS rate was predominantly owed to an increase in Robson group 5 (previous CS, singleton, cephalic, ≥37 weeks of gestation), and to a lesser extent to an increase in Robson group 2a (nulliparous, single cephalic, ≥37 weeks, induced), confirming the prominent role of the clinical management of women with a previous CS. Pooling of the 10 Robson groups into five was performed in this study, precluding a detailed comparison to our data [24]. Finally, Hehir et al. [27] in their longitudinal study used United States vital statistics data 2005–2014 and retrospectively classified all births according to the TGCS in five time periods. They identified Robson group 5 as the largest contributor to the total CS rate [27]. However, issues about the data quality emerged [35], limiting the comparison to our data.

The analysis of national figures and aggregated data of unit A + B revealed a higher number of women in Robson group 8 (multiple pregnancies) and 10 (single preterm cephalic pregnancies) in the two units. We attribute this finding to the fact that both units, even though at different levels, serve an at-risk population. This pertains to the care of women with multiple pregnancies, with particular emphasis on the management of monochorionic dizygotic twin pregnancies; and to the clinical care of women with preterm labor, with particular emphasis on the management of extremely preterm births (both for unit A predominantly). Although the CS rate in these Robson groups was high, differences in the size of these groups usually do not contribute to the overall CS rate. Vogel et al. [20] in their comparison of CS rates in 21 countries and two periods of time, e.g., restricted their analysis to Robson group 1 to 5, arguing that Robson group 6 to 10 (breech, multiple pregnancy, abnormal lie, singleton preterm cephalic) includes only 15% of all cases and contributes to only 20% of the total CS rate [20]. This does not apply to the contemporary obstetric practice in Germany; here, 12.2% of cases (Robson group 6 to 10) contributed to 26.3% of the overall CS rate (21.3% of cases and 39.5% of the overall CS rate in unit A + B). For an appraisal of these differences, perinatal data are required to investigate whether the higher CS rate in these groups translates into a better perinatal outcome.

The smaller size of Robson group 1 and 3 (nulliparous, single cephalic ≥37 weeks of gestation, in spontaneous labor; and multiparous, respectively) for the aggregated data of unit A + B pointed to a difference in the patient population between Germany as a whole and unit A + B. Again, this difference may be owed to the fact that both units serve an at-risk population, even though to a different extent. Women without risk factors may opt to give birth preferentially in basic obstetric units which do not provide other facilities, e.g. a neonatal unit.

The lower CS rate in Robson group 1 (nulliparous, single cephalic ≥37 weeks of gestation, in spontaneous labor) for the aggregated data of unit A + B compared to national data revealed another difference in clinical practice. The lower emergency CS rate may have been owed to the fact that women with at-risk pregnancies booking at units A + B for delivery underwent a more detailed evaluation of the maternal and fetal wellbeing before the onset of birth; women with a high chance of requiring an emergency CS may have been triaged into Robson group 2 (induced or CS before labor).

The difference in the clinical practice of Robson group 4 (multiparous, single cephalic ≥37 weeks of gestation, induced or CS before labor) between Bavaria and the aggregated data of unit A + B (higher number of IoL in the latter) cannot be explained without additional patient data. Our hypothesis is that women in unit A + B had risk factors (e.g. age, body mass index, comorbidities) which prompted the obstetrician in charge to decide for IoL.

Regarding Robson group 2a (nulliparous, single cephalic ≥37 weeks of gestation, induced), CS rates in unit A + B were comparable to Bavarian data and data of the Norwegian, Irish and Slovenian departments (8.6–13.8%) [25]. However, a lower group size was reported in the study by Pyykönen et al. 2017 (4.0–8.7%) [24]. The CS rate after IoL in nulliparous women with term single cephalic pregnancy (Robson group 2a) showed wide variations. Whereas in unit A the CS rate was 38.4% (28% in unit B), and similar to the Irish center (30.2%), the CS rate after IoL in this Robson group was substantially lower in the Norwegian and Slovenian departments (19.6 and 23.0%, respectively) [25]. In Scandinavia, the CS rate in this Robson group ranged from 20.2 to 30.3% [24].

Likewise, the size of Robson group 2b (prelabor CS in nulliparous women with singleton cephalic pregnancy ≥37 weeks of gestation) differed considerably between unit A + B, Bavaria (2.4–3.7%) and its neighboring countries. There, the group size was reported between 0.3 and 1.5% [24], [25].

Thus, differences in clinical practice in Robson group 1 and 2, representing all nulliparous women with singleton pregnancies ≥37 weeks of gestation, became apparent. An explanation of the high emergency CS rate after IoL in unit A and unit B may be differences in the risk profile of the cases. A reference to the maternal and fetal outcome is required for further interpretation of the data.

Comparison between unit A and unit B

The nearly 50% higher CS rate in unit A compared to unit B illustrates that a comparison of total CS rates is not sufficient for an appraisal of the respective obstetric practice.

In both units, nulliparous women with single cephalic pregnancy ≥37 weeks of gestation (Robson group 1 + 2) constituted one third of the population (34.7% in unit A and 34.8% in unit B). However, the ratio between group 1 and 2 was differing. Whereas in unit B the ratio was similar to the figure mentioned by the WHO manual [16] and was corresponding to the ratio in three European obstetric units [25], the 1:1 ratio in unit A cannot be explained without additional patient data. We attribute this finding to epidemiological differences; unit A is caring for women with preexisting diseases and serves as a center for prenatal diagnosis, which increases the chance for nulliparous women to undergo IoL or elective CS. The same applies for Robson group 3 and 4, where internationally the ratio is supposed to be larger than 2:1 [16], [25]. This ratio amounted to 2.9:1 in unit B, but only 1.7:1 in unit A.

For both units, Robson group 5 (previous CS, single cephalic, ≥37 weeks) was the largest single absolute and relative contributor to the CS rate, followed by Robson group 10 (preterm singleton cephalic) and 2a (nulliparous, term single cephalic, IoL). To further investigate the difference in proportions between the two units, nonparametric bootstrap calculations were performed, confirming the lack of a difference in the relative frequency of this Robson group between the two units, whereas in the majority of cases the second and third most relative frequent Robson group was different. In contrast, Vogel et al. [20] in their analysis of 21 countries and two time periods found Robson group 1 + 2 (all nulliparous, term, single cephalic pregnancies) as the largest single contributor to the CS rate, followed by Robson group 5 [20].

The CS rates for Robson group 5 in unit A and unit B revealed differences in the clinical practice of the handling of births in woman after CS. Both units exceeded the recommended CS rate of 50–60% [16]. Corresponding figures for Ireland and Slovenia were high as well (60.9% and 74.7%) [25]. In contrast, figures in Scandinavia complied with the WHO recommendations, ranging from 41.9% in Norway to 48.9% in Sweden [24]. Interestingly, a temporal change could be observed during the study period; here, increases (like in Denmark from 46.3 to 59.1%) as well as declines (like in Finland from 45.8 to 42.6%) in the repeat CS rates occurred [24]. These data illustrate the large variations in the clinical management of women with previous CS. We hypothesize that non-medical causes may have contributed to the decision between trial of labor and elective repeat CS. These may have included, among others, women’s expectations as well as providers’ fear of litigation [11]. When aiming for a reduction in the overall CS rate, a detailed examination of this group is required for every obstetric unit.

Finally, the significant differences in Robson group 10 (singleton, cephalic, preterm) between unit A and unit B – including group size, group CS rate, and absolute and relative contribution to the total CS rate – are noteworthy. Compared to national data, the group size in unit A was more than twice the national size. An explanation for this finding is the fact that unit A is a regional center for prenatal diagnosis and therapy, with a high proportion of pregnancies characterized by fetal malformations and fetal growth restriction; additionally, unit A serves as a referral center for maternal complications of pregnancy.

Limitations

With the available data, causes for the observed differences in CS rates cannot be explained. The differences may be a result of differences in the study population rather than differences in the clinical practice. Robson group 10 e.g. does not allow for a distinction between the various degrees of prematurity; in Robson group 5, cases with one and with multiple previous CS are pooled. The creation of additional Robson subgroups may allow for a more detailed analysis [14], [29]. Lastly, indications for prelabor CS (Robson groups 2b and 4b) may have differed according to the hospital’s level of care, with women with preexisting conditions or fetuses with prenatally detected abnormalities seeking delivery in the higher-level hospital. To verify this hypothesis, obstetric and perinatal data need to be incorporated and analyzed [19].

Our comparison was restricted to reports from other high-income countries. We felt that the comparison with the obstetric population in low- and medium-income countries [20] would not have made a meaningful contribution to our research question.

Compared to other publications [18–20, 24, 25, 27, 29] the size of or study group was small. Since boostrapping revealed stability of our major results we are confident that our sample size is adequate.

Finally, the application of the TGCS does not take the maternal and perinatal outcome into consideration. For this purpose, maternal, fetal and obstetric data need to be recorded, and core outcomes have to be agreed upon. Thus, associations between CS rates and quality of care can be established.

Conclusions

Our analysis of CS rates according to the TGCS revealed conformities and differences. With respect to the comparison between the two obstetric units and national data, differences could be attributed largely to the type of population served. The comparison between the two units revealed both, differences in the type of population and in clinical practice. The latter pertains to the management of birth after CS and IoL in nulliparous women in particular. Since these represent the most relative frequent Robson groups, a change in clinical practice may have a high impact on the CS rates. Our results may serve as a foundation for internal audits of each unit. The demonstration of differences in clinical practice may stimulate inter-hospital discussions, which may offer an opportunity for reevaluation of standard operating procedures, thereby curbing CS rates of each respective unit.

Corresponding author: Christina Pulvermacher, Department of Obstetrics and Prenatal Medicine, University Hospital Bonn, Venusberg-Campus 1, 53127 Bonn, Germany, Phone: +49 176 21990602, E-mail:

  1. Research funding: None declared.

  2. Author contributions: All authors have accepted responsibility for the entire content of this manuscript and approved its submission.

  3. Competing interests: Authors state no conflict of interest.

  4. Informed consent: Informed consent was obtained from all individuals included in this study.

  5. Ethical approval: The Ethics Committee of the University Bonn Medical School approved the research project (number 261/17).

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Received: 2020-10-24
Accepted: 2021-03-18
Published Online: 2021-04-08
Published in Print: 2021-09-27

© 2021 Walter de Gruyter GmbH, Berlin/Boston

Articles in the same Issue

  1. Frontmatter
  2. Editorial
  3. Introduction to the cesarean section articles
  4. Highlight Section: Cesarean Section
  5. Three kinds of caesarean sections: the foetal/neonatal perspective
  6. The neonatal respiratory morbidity associated with early term caesarean section – an emerging pandemic
  7. Vaginal birth after cesarean (VBAC): fear it or dare it? An evaluation of potential risk factors
  8. Nationwide implementation of a decision aid on vaginal birth after cesarean: a before and after cohort study
  9. Induction of labor at 39 weeks and risk of cesarean delivery among obese women: a retrospective propensity score matched study
  10. Cervical ripening after cesarean section: a prospective dual center study comparing a mechanical osmotic dilator vs. prostaglandin E2
  11. An evidence-based cesarean section suggested for universal use
  12. Online survey on uterotomy closure techniques in caesarean section
  13. Analysis of cesarean section rates in two German hospitals applying the 10-Group Classification System
  14. Reviews
  15. Pregnancy in incarcerated women: need for national legislation to standardize care
  16. Imaging diagnosis and legal implications of brain injury in survivors following single intrauterine fetal demise from monochorionic twins – a review of the literature
  17. Mini Review
  18. Professionally responsible management of the ethical and social challenges of antenatal screening and diagnosis of β-thalassemia in a high-risk population
  19. Opinion Paper
  20. Teaching and training the total percutaneous fetoscopic myelomeningocele repair
  21. Corner of Academy
  22. Chronic hypertension in pregnancy: synthesis of influential guidelines
  23. Original Articles
  24. The effects of pre-pregnancy obesity and gestational weight gain on maternal lipid profiles, fatty acids and insulin resistance
  25. Determination of organic pollutants in meconium and its relationship with fetal growth. Case control study in Northwestern Spain
  26. Betamethasone as a potential treatment for preterm birth associated with sterile intra-amniotic inflammation: a murine study
  27. Diagnostic accuracy of modified Hadlock formula for fetal macrosomia in women with gestational diabetes and pregnancy weight gain above recommended
  28. Vasa previa: when antenatal diagnosis can change fetal prognosis
  29. Mode of delivery and adverse short- and long-term outcomes in vertex-presenting very preterm born infants: a European population-based prospective cohort study
  30. Short Communication
  31. Reference ranges for sphingosine-1-phosphate in neonates
https://doi.org/10.1515/jpm-2020-0505
Keywords for this article
10-Group Classification System; audit; cesarean section rates; cesarean section statistics; cesarean section trends; delivery; health care; quality indicators; Robson classification; TGCS

Articles in the same Issue

  1. Frontmatter
  2. Editorial
  3. Introduction to the cesarean section articles
  4. Highlight Section: Cesarean Section
  5. Three kinds of caesarean sections: the foetal/neonatal perspective
  6. The neonatal respiratory morbidity associated with early term caesarean section – an emerging pandemic
  7. Vaginal birth after cesarean (VBAC): fear it or dare it? An evaluation of potential risk factors
  8. Nationwide implementation of a decision aid on vaginal birth after cesarean: a before and after cohort study
  9. Induction of labor at 39 weeks and risk of cesarean delivery among obese women: a retrospective propensity score matched study
  10. Cervical ripening after cesarean section: a prospective dual center study comparing a mechanical osmotic dilator vs. prostaglandin E2
  11. An evidence-based cesarean section suggested for universal use
  12. Online survey on uterotomy closure techniques in caesarean section
  13. Analysis of cesarean section rates in two German hospitals applying the 10-Group Classification System
  14. Reviews
  15. Pregnancy in incarcerated women: need for national legislation to standardize care
  16. Imaging diagnosis and legal implications of brain injury in survivors following single intrauterine fetal demise from monochorionic twins – a review of the literature
  17. Mini Review
  18. Professionally responsible management of the ethical and social challenges of antenatal screening and diagnosis of β-thalassemia in a high-risk population
  19. Opinion Paper
  20. Teaching and training the total percutaneous fetoscopic myelomeningocele repair
  21. Corner of Academy
  22. Chronic hypertension in pregnancy: synthesis of influential guidelines
  23. Original Articles
  24. The effects of pre-pregnancy obesity and gestational weight gain on maternal lipid profiles, fatty acids and insulin resistance
  25. Determination of organic pollutants in meconium and its relationship with fetal growth. Case control study in Northwestern Spain
  26. Betamethasone as a potential treatment for preterm birth associated with sterile intra-amniotic inflammation: a murine study
  27. Diagnostic accuracy of modified Hadlock formula for fetal macrosomia in women with gestational diabetes and pregnancy weight gain above recommended
  28. Vasa previa: when antenatal diagnosis can change fetal prognosis
  29. Mode of delivery and adverse short- and long-term outcomes in vertex-presenting very preterm born infants: a European population-based prospective cohort study
  30. Short Communication
  31. Reference ranges for sphingosine-1-phosphate in neonates
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