Dissecting the current caesarean section rate in Shanghai, China

The high caesarean section (CS) rate has been of great public concern around the world. Yet, large-scale studies of dissecting such a high CS rate are few in the Chinese population. We carried out a cross-sectional survey randomly selecting 10,855 births from 20 hospitals in Shanghai from January to June, 2016. Labor and delivery information was extracted from medical records. The Robson classification system for CS was used to classify all women into ten groups. The overall CS rate was 41.5%. Prelabor CS in nulliparous, term singleton vertex women was the predominant contributor (37.4%) to the total CS and accounted for the second highest proportion of total births (15.5%) in all hospital types. The vast majority of women with a previous CS had a repeat CS (96.6%). CS rate was still high in Shanghai. Nulliparous women in low risk and having CS before labour, often without any medical indication, was a major contributor to the high CS rate.


Results
Among the 20 hospitals, 11 were located in the city proper (Fig. 1). 12 hospitals delivered fewer than 5,000 births; 4 delivered between 5,000 and 10,000 births; and 4 had more than 10,000 deliveries in 2016. Table 1 presents the basic characteristics of the subjects by hospital type. Nearly 80% of women were 25 to 35 years old and 54.2% had medical insurance. Seven in ten pregnant women had a college or higher degree, and office worker (60.2%) was the most common occupation, followed by unemployed (25.8%) and researcher/teacher/doctor (10%). Nearly sixty-five percent of pregnant women were nulliparous; 13.9% were with previous CS; 95.6% had cephalic presentation, and 1.7% were multiple gestations. The average prepregnancy body mass index (BMI) of the women was 21.6 ± 3.3 kg/m 2 , with underweight, normal weight, overweight and obese women accounting for 15%, 51.4%, 16.9%, and 16.8%, respectively (based on WHO 2000 Asian BMI cut points) 6 . Pre-pregnancy hypertension, diabetes, heart disease and kidney disease were found in 0.6%, 0.2%, 1.0% and 0.2% of women, respectively. Table 2 shows the indications of CS in different hospital types in Shanghai. The top six indications were repeat CS, fetal distress, patient request, non-cephalic fetal presentation, suspected macrosomia, and cephalopelvic disproportion, accounting for 76% of all CS. The rest of indications and unknown indications accounted for 23.7% and 0.3%, respectively (Detailed list of indications are listed in Appendix). Repeat CS was the first CS indication  in all types of hospitals, accounting for 20.4%, 32.0%, 26.2% and 34.9% of the total CS, respectively. The order and contribution of other indications varied among the hospital types. For example, patient request was the number two reason in the secondary maternity hospital, accounting for 13.9% of the total CS while fetal distress was the number two reason all other types of hospitals, accounting for 18.1%, 16.1%, and 21.0% of the total CS, respectively. Table 3 shows the CS rate and proportion in subgroups by RTGCS. Nulliparous, term singleton vertex women in spontaneous labour (NS group) accounted for the highest proportion of total births (30.7%), followed by nulliparous, term singleton vertex women with CS before labour (NC group) (15.5%). Term, singleton, vertex women with previous CS (PC group) accounted for 11.1% of total birth. The majority of pregnant women (96.6%) with a previous CS (PC group) had repeat CS. Nulliparous, term singleton vertex women in spontaneous labor (NS groups) had a relatively lower total CS rate (6.9%) than in induced labour (NI groups) (19%). Nulliparous, term singleton vertex women with CS before labour (NC group) was the predominant contributor to the total CS (37.4%), followed by term singleton vertex women with previous CS (PC group, 25.9%). Table 4 further shows the CS rate and proportion in different hospital types by RTGCS. The tertiary maternity hospital had the lowest CS rate in nulliparous, term singleton vertex women in spontaneous labor (NS groups) (3.13%) and in induced labor (NI group) (13.6%), but accounting for the highest contributor to the total CS in nulliparous, term singleton vertex women with CS before labour (NC group) (44.6%). Otherwise, CS rate in term singleton vertex women with a previous CS (PC group) was also the lowest in the tertiary maternity hospital than other types of hospitals (94.21%). Table 5 shows the mode of delivery according to birth-weight category by RTGCS. The CS rate increased with increasing birth-weight above 2500 g for nulliparous/multiparous, term singleton vertex women in spontaneous labor (NS and MS groups, P < 0.01), and pregnant women with a previous CS (PC group). The CS rate was only 36.7% in neonatal birth-weight of 3000-3499 g, compared with 61.9% in neonatal birth-weight above 4000 g. For each birth-weight category, the CS rate was higher in nulliparous/ multiparous, term singleton vertex women in induced labour (NI/MI group) than in spontaneous labor (NS/MS group).

Discussion
Our study found that CS rate in Shanghai, China, was still very high, at 41.5%. Nulliparous, term singleton vertex women with CS before labour (NC group) constituted 15.5% of total births and was the largest contributor to the total CS in all hospital types (37.4% overall). The majority of women with previous CS had a repeat CS (96.6%). Nulliparous, term singleton vertex women in induced labour (NI groups) had a relatively higher total CS rate than in spontaneous labor (NS groups) (19% vs 6.9%). The tertiary maternity hospital had the lowest CS rate in nulliparous, term singleton vertex women in spontaneous labor (NS groups) (3.13%) and in induced labor (NI group). The top six indications for CS were repeat CS, fetal distress, patient request, non-cephalic fetal presentation, suspected macrosomia and cephalopelvic disproportion. In nulliparous and multiparous, term singleton vertex women in spontaneous labor (NS and MS groups), and pregnant women with a previous CS (PC group), the CS rate increased consistently with increasing neonatal birth weight above 2500 g. Nulliparous, term singleton vertex women with CS before labour (NC group) contributed to the most CS deliveries (37.4%), ranging from 27.5% in secondary general hospitals to 44.6% in tertiary maternity hospitals. This proportion is 10 times higher than 3.5% in Netherlands 7 . There are two possible explanations. First, the high proportion of CS in NC group (44.6%) among total CS in tertiary maternity hospitals could be explained by the low CS rate in NS and NI group and consequent low proportion of total CS that they represent. Second, the Chinese government had abolished the "One-Child Family" restriction and permitted the "Two-Child Family" policy in December 2015. Anecdotal evidence suggests that after the change of family planning policy, many nulliparous women are trying to give vaginal birth in consideration of future pregnancies. However, our study showed that CS on patient request is still very common, accounting for 10.7% of all CS. Although this proportion has declined substantially comparing to previous reports 8 , it is still a major contributor to the high CS rate in Shanghai.
We found that repeat CS has actually become the leading cause for the high CS rate in Shanghai. This is mainly because CS has been popular in China in the past 20 years 9 , resulting in a high proportion of multiparas with a scarred uterus. The recent change in family planning policy to allow two children per family may exacerbate this situation. As more women with previous CS than ever become pregnant and 96.6% of them chose to have repeat   CS, the CS in multiparous women may actually increase. Despite that the CS rate in nulliparas could decline, repeat CS may counterbalance. Consequently, the total CS rate may remain unchanged or even increase. It should be noted that although numerous studies have demonstrated that vaginal birth after previous CS (VBAC) is a safe alternative to repeat CS in carefully selected patients 10 , the urgency of intervention in patients undergoing a trial of labor needs to be in high alert as the avoidance of emergency CS might pose risks for mother and fetus, and increase requirements of general anesthesia and problems in futures pregnancy 3 . Thus, mastering and understanding the indications and contraindications of the trial of labour after caesarean (TOLAC) was the key to success 11 .
Abnormal fetal heart rate was the second leading indication for CS in Shanghai. Sixteen percent of CS deliveries were reported to be due to "fetal heart rate abnormality or fetal distress". The routine use of continuous fetal heart rate monitoring perhaps permitting longer 2 nd stage of labor as long as both progress in descent was being made and fetal safety were assured 12 . However, the routine use of cardiotocography for low-risk women on entrance to the labor ward has been associated with an increase in CS rates and no improvement in perinatal outcomes 13 . The poor sensitivity and specificity of electronic fetal heart rate monitoring often led to false positives when predicting fetal abnormalities. In addition, physician's judgement on the fetal electrocardiogram is often subjective. Therefore, standardized training for obstetricians and reducing CS based on erroneous judgement play a vital role.
Birth weight is an important determinant of mode of delivery 5 . In our study, the CS rate increased consistently with each 500 g increase in neonatal birth weight above 2500 g in term singleton vertex women in spontaneous labor and pregnant women with a previous CS. For each birth-weight category, the CS rate were higher in nulliparous/multiparous, term singleton vertex women in induced labour (NI/MI group) than in spontaneous labor (NS/MS group). This was consistent to other research results 5 .
In Shanghai, the CS rate was 6.9% in nulliparous, term singleton vertex women in spontaneous labor (NS groups) and the corresponding CS rate was 3.1% in the tertiary maternity hospitals. These seemingly very low rates may be attributable to the very high prelabor CS rate, i.e., only women with good conditions for labor had a trial of labor. These findings are consistent with that in a Brazil study where the corresponding CS rate was 6.3% when neonatal birth weight in 3000 g-3499 g 5 .
Our study has two limitations. First, we have not expert review of each CS record for the information of the underlying circumstances and indications for cesarean section. A more detailed secondary analysis, of the underlying circumstances and indications for cesarean section is needed to operationally identify possible remedial measures in modifiable groups which can reduce the caesarian section rates. Second, we have not investigated the maternal and fetal morbidity and mortality, and their relationship with delivery mode and RTGCS due to lack of detailed clinical information on the causes of CS. Previous studies showed that the rate of CS was positively associated with severe maternal and fetal morbidity and mortality, even after adjustment for risk factors 14,15 . This finding should be confirmed in the future.
In summary, CS rate was still high in Shanghai. Nulliparous women in low risk (with term, term singleton vertex) and having CS before labor, often without any medical indication, was a major contributor to the high CS rate. The tertiary maternity hospital had the lowest CS rate in nulliparous women. Our finding may help us to understand the target for reducing CS rate in Shanghai, China.