The global cesarean delivery (CD) rate has experienced a 100% increase over the past 15 years, reaching 21%, and it continues to rise at an annual rate of 4%.1 The increasing rate of CDs is a substantial concern in many societies.1 Factors such as medical advancements, changes in clinical practices, and shifts in patient preferences have contributed to this increasing rate.2 One specific aspect that has garnered attention is the rise in caesarean deliveries performed on maternal request (CDMR).3 CDMR refers to the practice of performing caesarean deliveries in the absence of medical indications, solely based on the mother's preference or request.45

Vaginal delivery (VD) is preferred over CD for women with no specific obstetrical indications in pregnancies following a successful VD, primarily because of concerns about potential complications arising from the surgical procedure.67 In addition, children who are delivered via CD have an increased risk of several complications such as respiratory distress syndrome, chronic health complications (asthma, obesity, diabetes, and autoimmune disorders), and microbiome alterations.891011

Women who have successfully undergone a VD often experience smoother subsequent deliveries because of their previous experience. Additionally, potential risks are associated with caesarean delivery, which highlights the importance of understanding the factors influencing the choice of CDMR following a successful VD. Begum noted that, on average, 6% of all cesarean sections were performed due to maternal request, a figure that aligns closely with the 5.5% global incidence rate of CDMR in high-income countries, as found in a recent research.12 This rise in CDMR is consistent with findings from the United States13 and Scandinavian nations.1415 A study based on the International Classification of Diseases (ICD)-10 code O82 conducted in Sweden indicated a tripling of CDMR rates from 1997 to 2006.14 Furthermore, a trend analysis from Ontario, Canada, revealed a consistent increase in CDMR, maintaining a rate of 4% of all cesarean sections from 2012 to 2018.16 Despite being relatively minor, the rising trend of CDMR in Australia raises concerns.17

Given the rise in CDMR and the ongoing debate about the validity of this birthing method, investigating the reasons behind such choice and its potential consequences is crucial. However, to date, limited research has been conducted on women who opt for CDMR after previous successful VD. This knowledge gap reinforces the need for more comprehensive studies to assess the factors that drive this decision. This information is essential to shed light on whether CDMR is a suitable choice, and whether the consequences associated with CDMR are adequately understood. Therefore, this study aimed to examine the underlying reasons that lead mothers to choose a CDs in subsequent pregnancies following a VD.

Women (545,217) with a history of two singleton live births between 2011 and 2020 were included in this study. Additionally, women who exhibited clear medical indications for CD and those who exhibited relative indications that were anticipated to have led to a CD for maternal safety despite the option of TOL, such as HELLP syndrome, eclampsia, fetal death in utero, abnormal bleeding, and maternal coagulopathy, were also excluded. The final analysis was conducted on a cohort of 372,749 women (Fig. 1). Ultimately, the cohort was divided into two groups: TOLS group, consisting of 368,311 women who opted for TOL during their second pregnancy, and CDRS group, comprising 4,438 women who underwent CDMR.

Table 1 compares the baseline characteristics of the two groups. CDRS group were older during both their first and second deliveries, had a longer interval between the two childbirths, and had babies with lower birth weights, compared to those who opted for TOL. Additionally, a higher prevalence of preexisting diabetes and hypertension was observed before the first pregnancy, along with a greater incidence of pregnancy complications during the first trimester and a higher frequency of postpartum hemorrhage was observed in the CDRS group. The prevalence of diabetes and hypertension remained elevated before the second pregnancy and higher incidences of gestational diabetes mellitus (GDM) and hypertensive disorders during pregnancy (HDP) were observed.

Upon detailed comparison, no significant differences were observed between the TOLS group and CDRS group in the occurrence of labor dystocia, intrapartum hemorrhage, or fetal distress during the first intrapartum period. However, compared with the TOLS group, the CDRS group had a higher frequency of traumatic events during the first delivery, along with a greater occurrence of surgical vaginal deliveries. Furthermore, an increased prevalence of history of embolism was observed in the CDRS group (Table 2).

When comparing the occurrence of pregnancies with abortive outcomes between the first and second pregnancies, there was a higher incidence of an ectopic pregnancy history in the CDRS group. Additionally, a large number of cases involving abnormal products of conception and complications arising from ectopic or molar pregnancies were observed. Moreover, an increased frequency of a history related to spontaneous abortion and induced termination was noted in the CDRS group (Table 3).

When conducting regression analysis for the CDRS group, the following factors were found to increase the risk of opting for CDMR: each additional year of age at the second pregnancy (adjusted odds ratio (aOR), 1.06; 95% confidence interval [CI], 1.05–1.07), each additional year of pregnancy interval between the first and second pregnancies (aOR, 1.32; 95% CI, 1.29–1.35), a history of pre-existing hypertension before the first childbirth (aOR, 1.76; 95% CI, 1.17–2.65), GDM during the first pregnancy (aOR, 1.19; 95% CI, 1.05–1.36), HDP (aOR, 1.33; 95% CI, 1.06–1.67), preterm labor (PTL) during the first pregnancy (aOR, 1.57; 95% CI, 1.32–1.86), postpartum hemorrhage (aOR, 1.33; 95% CI, 1.21–1.47), traumatic event during delivery of the first child (aOR, 1.19; 95% CI, 1.12–1.28), surgical VD during the first childbirth (aOR, 1.29; 95% CI, 1.19–1.40), and pregnancies with abortive outcomes between the first and second pregnancies (aOR, 1.18; 95% CI, 1.08–1.29) even after adjustment. Furthermore, women who had pre-existing diabetes (aOR, 1.53; 95% CI, 1.24–1.89), pre-existing hypertension (aOR, 1.69; 95% CI, 1.26–2.26), GDM (aOR, 1.23; 95% CI, 1.11–1.37), or HDP (aOR, 2.57; 95% CI, 2.24–2.94) during the second pregnancy continued to exhibit an increased risk of opting for CDMR even after adjustment (Table 4).

The main findings of this study were as follows: 1) in the CDRS group, women were older during both their first and second deliveries, had a longer interval between the two childbirths, and second-born infants had lower birth weights compared to the TOLS group; 2) women who wanted to deliver by CD after VD also had a history of PTL and traumatic or surgical VD during the first pregnancy, history of abortion, and comorbidities (GDM and HDP) during subsequent pregnancies.; 3) In South Korea, the incidence of CDMR has been increasing annually (Table 5, Supplementary Fig. 1).

The rising incidence of CD births is a global trend, and has evolved into a substantial global healthcare concern.1819 Viewed from a broader perspective, CDs are often linked to elevated surgical risks, both in the current pregnancy and in subsequent ones, when compared to natural vaginal births.202122 From the standpoint of newborns, opting for CDs may potentially contribute to reducing the occurrences of birth trauma or stillbirth rates.2324 However, such deliveries could lead to a higher incidence of initial respiratory difficulties.25 Since the emergence of CDMR, numerous studies have been conducted to investigate the reasons behind mothers' initial preference for CDs and the associated incidence and outcomes.262728 However, research analyzing why women who have previously undergone vaginal deliveries might opt for CDs in subsequent pregnancies, even in the absence of indications is lacking. This study aimed to address this gap.

In previous studies investigating the causes of CDMR, potential factors that have been suggested as contributors include a personal history marked by distressing experiences, such as unfavorable obstetric outcomes, apprehension surrounding the process of labor and childbirth, and concerns related to pain.2930 Our data suggest that women opting for CDMR in their second pregnancy tended to be older during both the first and second deliveries, with a longer interval between childbirth, and had lower birth weight second-born infants. Pre-existing conditions such as diabetes and hypertension were more prevalent before the first and second pregnancies, along with increased pregnancy complications in the first and second pregnancies. Comparing the groups in more detail, the CDMR group showed a higher rate of traumatic events or embolism history during the first delivery, more surgical vaginal deliveries, and a greater history of pregnancies with abortive outcomes between the first and second pregnancies compared to those of the TOL group.

While the American College of Obstetricians and Gynecologists emphasizes that VD is considered safe and recommended in the absence of maternal or fetal indications for CD, the decision between CDMR and planned VD lacks definitive evidence favoring one over the other.29 To date, evidence to fully establish the safety of CDMR is insufficient to provide firm recommendations. Therefore, understanding the factors that influence maternal choices and character traits is crucial, as explored in this study. These factors could impact the safety of CDMR and shed light on the factors that may guide maternal decision-making. Especially for women who give birth to their first child through VD, an expectation of smoother subsequent vaginal deliveries exists. Therefore, identifying the factors that contribute to this choice and their underlying reasons to ensure appropriate counseling is essential.

Managing the appropriate use of CD is considered a crucial global issue.3132 Underusing CD can lead to an increase in perinatal mortality and morbidity, while excessive CD can result in short-term and long-term complications and unnecessary resource wastage.3334 Therefore, ensuring an appropriate level of CD is important.

Choosing to perform a CD after a VD is another significant issue, and research that identifies clinical characteristics of patients, such as in this study, can be a valuable part of global efforts to reduce unnecessary CDs. Using the characteristics identified in this study, clinical interventions can be applied to patients who desire a CD after a VD at the appropriate time through induction or labor support. It can also serve as a starting point for research aimed at safe VD, contributing to the application of studies for successful VD.3536 Additionally, non-clinical interventions can provide support to patients through healthcare systems and establish a foundation for continuous support during pregnancy through human relationships or education.

As there is currently no specific ICD code for CDMR, we were able to conduct a comprehensive analysis using large-scale data by utilizing procedural codes related to the TOL groups in the national databases. Although medical record reviews have limitations in accurately identifying the reasons for choosing CDs, conducting additional qualitative studies would provide valuable insights. These qualitative studies could help guide and enhance precise counseling by delving into the reasons behind the decision to perform a CD. Examining these viewpoints will play a crucial role in revealing the various attributes among women opting for CDMR. In addition, it contributes to ensuring fair and impartial healthcare practices in obstetrics.

This study was the first to explore the reasons for CD without indications following VD. Using the ICD codes, this study objectively examined a spectrum of conditions and situations that may arise before and after childbirth. By leveraging this extensive dataset, we were able to identify noteworthy variations in the characteristics between women who chose CDMR and those who pursued a TOL trial after a previous VD, wherever such distinctions were present. However, this study had several limitations. First, because this was a retrospective study, further prospective research is necessary. Moreover, owing to the absence of specific diagnostic codes for CDMR, instances in which procedural or indication-related codes were omitted could potentially lead to disparities between the observed incidence and true occurrence of CDMR. Another limitation of this study is that although estimated fetal weight is a crucial factor in deciding the mode of delivery, due to the data structure and retrospective nature of this analysis, we were unable to compare the estimated fetal weight. Finally, caregiver bias occurs when healthcare providers' personal beliefs and experiences influence their medical decisions. This bias can affect treatment choices and potentially skew study outcomes. Acknowledging the potential impact of caregiver bias is a recognized limitation of the study. Nevertheless, we made efforts to improve accuracy by utilizing procedure codes related to pain management or induction during intrapartum.

The choice of CDMR for a second pregnancy after successful VD for the first one has been increasingly prevalent among women with specific demographic characteristics, obstetric histories or obstetric complications in the subsequent pregnancies. Despite the limitations of our study, considering the potential surgical complications and neonatal respiratory issues that can arise from CD, counseling mothers thoroughly regarding the underlying reasons is crucial.