This study investigated geographic variation in cesarean section rates in Korea and its factors using the 2013 National Health Insurance Database in Korea. The overall cesarean section rate in Korea was 364.6 cases per 1000 live births. Given the range of value of each variable and the size of the coefficient value, the deprivation index score showed a strong positive association with the cesarean section rate, while the hospital obstetrician density and hospital bed density showed negative associations. Average maternal age and total fertility rate showed negative relationships with the cesarean section rate.
Korea’s cesarean section rate was high compared with other countries as already shown in the other source [31]. Often, the increasing age of mothers is cited as a reason for this. However, despite the marked aging tendency of mothers in Korea, the age distribution of Korean mothers cannot be considered old when compared with other developed countries [32, 33], and the cesarean section rates were even higher in the 2000s when the mothers were relatively younger. Several factors could have contributed to the high cesarean section rates. From the mothers’ side, the convenience which cesarean section can provide could have been highly regarded [34], especially among working women whose numbers have been on a continuous rise [35]. For mothers to reconsider the cesarean, it is too accessible in terms of both expense and service supply. Additionally, the widespread practice of fixing the date of the birth in Korea for the purpose of giving the child a fortune could have precipitated the choice of cesarean section. Most of all, obstetricians in Korea are in a position that gives them little motivation to dissuade patients from cesarean section. Due to the increasingly high risk of medical litigation and low fee schedule for vaginal delivery, obstetricians have little reason for promoting vaginal delivery and risking the legal and financial problems [16]. Moreover, the decline in the number of obstetricians makes it more difficult for them to deal with untimely delivery, and this eventually leads to the preference for the mode of delivery for which scheduling is possible. The decreasing availability of obstetric facilities, especially in rural areas, could have also precipitated the use of cesarean section by reducing the opportunities for prenatal care [36].
Concerning geographic variation, the highest cesarean section rate was about three times that of the lowest district. This suggests that the likelihood of having a cesarean section can differ widely according to where the mothers live. Our further analysis provides a more elaborate account of how the regional characteristics affect the cesarean rates.
The positive association between the deprivation index score and cesarean section rate indicates that the mothers in more disadvantaged areas are more likely to have a cesarean delivery. This can be discussed from the regional and individual point of view. First, the poor regional circumstances could have caused its residents to be more susceptible to perinatal problems by its direct impact on health and by poor access to care. This is relevant given the sharp decrease in obstetricians in remote and rural areas in Korea. Our results, which showed an inverse relationship between the number of hospital obstetricians and cesarean section rates, also support this. In addition, as the areas with high deprivation scores have relatively fewer obstetricians, it would be difficult for suppliers to engage in deliveries during the night. As a result, they are more likely to encourage pregnant women to have a cesarean section.
Second, considering that the deprivation index is an aggregate index of individual socioeconomic conditions, the relationship between the deprivation index score and cesarean section rate can largely be explained as the relationship between the socioeconomic conditions and the likelihood of getting a cesarean section. In the past, the higher level of education and income was related to a higher likelihood to receive a cesarean section [37], and this tendency is still observed in less developed countries [38,39,40]. However, in recent studies in the US and other European countries, a negative relationship between the socioeconomic conditions and the use of cesarean section has been reported [41,42,43]. This change in the influence of socioeconomic conditions on the use of cesarean section was clearly observed in Korea over the past decades [12, 44]. Our results show that now in Korea, the cesarean section is being more frequently performed among those in the regions with less affluent conditions. In the past, the cesarean delivery was a medical procedure which seemed more sophisticated and was expensive; therefore, it was an available option for only those who could afford it [44]. But the cost of cesarean section declined, it became common, and greater recognition of its risks with increasing preference for the less artificial way of delivery could have reduced the preference for cesarean sections [15]. However, the reversal of the relationship between income and cesarean section rates is also likely to be related to the regional supplier factors.
The negative relationship between the number of hospital obstetricians and cesarean section rates can be one explanation. This shows that mothers in the areas with less hospital obstetricians are more likely to have cesarean sections. Considering that one quarter of all districts were left without health care facilities for child delivery for years [45], we can suppose that the lack of obstetric facilities could have negatively affected the access both to pre- and perinatal care, which led to higher cesarean section rates.
The number of hospital beds had a negative association with the cesarean section rates. This suggests that the regions with more hospitals offer favorable conditions for vaginal delivery and that the impact of hospital beds still remains even after allowing for the influence of the number of obstetricians. In viewing the oversupply of hospital beds in Korea [46], our results indicate that the oversupply is not universal among regions. Some regions may not benefit from the increase in hospital beds but rather suffer from the consequence of the lack of them.
The average maternal age had a negative association with cesarean section rate, and this relationship was distinctive in the standardized rate. This phenomenon is suggestive of possibilities: First, the overall cesarean section rate is lower in the regions with higher average maternal age, and, second, the cesarean section rate among the elderly mothers is lower in the regions with higher average maternal age. The cesarean section is more frequently performed among the aged mothers. The mothers in the urban and affluent areas are less likely to receive a cesarean section, and the average maternal ages in such regions tend to be higher than those in rural or deprived areas, which leads to a negative relationship between average maternal age and cesarean section rate. In addition, when comparing elderly mother groups, the urban and affluent areas have lower cesarean section rates. That is why the decreasing effect of average maternal age on the cesarean section rate is more distinctive in the standardized rates.
The inverse relationship between the total fertility rate and cesarean section rate shows that the scarcer the child delivery is, the more likely the cesarean section happens. Considering that this impact exists after the adjusting factors such as the average maternal age, density of hospital obstetricians, and hospital beds, we can suppose that the rarity of birth delivery in a region has its own impact of bringing down the proportion of natural birth. It is highly probable that a region where there are fewer child deliveries is not an attractive place for an obstetric practice. This relationship between the fertility rate and obstetrician supply needs to be further scrutinized as this can lead to a vicious cycle.
There are some considerations that should be taken into account when interpreting the results of this study. First, the unit of analysis in this study is a region, and the independent variables concerning mothers’ characteristics are aggregate variables. Therefore, the impact of those aggregate variables should be differentiated from their individual counterparts. The inverse relationship between the average maternal age and cesarean section rates is an example which shows that the influence of variables of regional unit and an individual can differ. As most of the studies investigating the factors for cesarean sections were performed with an individual as a unit of analysis, such differences should be taken into consideration when comparing our results with prior studies. Second, in July 2013, the diagnosis-related group (DRG) based payment system was introduced to several procedures including cesarean section. Although the cesarean section rate in Korea has been on the rise despite the application of the DRG based payment [47], the new payment system could have affected the behaviors of the health care providers, which this study could not have captured. Third, our results showed the distinctive geographic pattern of the cesarean section rates. Though we explained such differences with various variables, there is more that can explain the phenomenon. For example, the different practice patterns among regions could have resulted from the differences in training among regional training hospitals. This training factor is very important considering that a large number of obstetricians in a region are likely to have been trained in hospitals in that region. Therefore, the training factor should be investigated in future studies. Lastly, as the cesarean section rate in Korea continued to rise after 2013 [48], our study needs to be updated with the recent data, and longitudinal studies would make a more accurate investigation of factors for cesarean section possible. However, as a regional variation study, this study has found two important factors of cesarean sections: regional socioeconomic conditions and obstetrician density, both of which had a negative relationship with cesarean section rates. While reflecting the specific condition in Korea where a shortage of obstetricians became a serious issue, our study also shows the differing status of cesarean section as a medium of child delivery.