Temporal trends and projections of caesarean sections in Brazil, its administrative macro-regions, and federative units

Trend studies on the model of birth in Brazil show a scenario of successive linear increases in cesarean rates. However, they ignore possible changes in the temporal evolution of this delivery modality. Thus, this study aimed to evaluate possible inflection points in cesarean rates in Brazil, its macro-regions, and federated units, as well as to estimate projections for 2030. A time series with information on cesarean sections from 1994 to 2019 from the SUS Department of Informatics was used. Autoregressive integrated moving average and joinpoint regression models were used to obtain cesarean rate projections and trends, respectively. Caesarean rates showed a significant upward trend over the 26 study years at all levels of aggregation. On the other hand, when considering the formation of segments, a stabilization trend was observed both in the country and in the South and Midwest regions, starting in 2012. Rates tended to increase in North and Northeast and significantly decrease in Southeast. Projections show that in 2030, 57.4% of births in Brazil will be cesarean, with rates higher than 70% in Southeast and South regions.


Introduction
Cesarean section is a life-saving procedure in specific obstetric circumstances and clinically recommended to prevent maternal and neonatal mortality.However, when performed without medical indications, it may be associated with negative short-and long-term outcomes for both mother and child 1,2 .
Maternal and fetal morbidity and mortality are higher after cesarean sections compared to vaginal delivery [3][4][5] .However, cesarean section is the most common major surgery in many countries.Its frequency increased in the last 30 years and currently exceeds by far the maximum percentage of 10% to 15% recommended by the World Health Organization (WHO) in a systematic review [6][7][8] .
The average overall cesarean rate is 21.1%, ranging from 5% in sub-Saharan Africa to 42.8% in Latin America/the Caribbean.Despite the high rates in many countries, cesarean section showed upward trends in all continents and sub-regions of the globe from 1990 to 2014 7 , 2000 to 2015 9 , and 1990 to 2018 8 .Its increase in the last three decades was higher in East and Western Asia and North Africa (44.9%, 34.7%, and 31.5%,respectively).In total, 38 million cesarean sections are estimated for 2030, which corresponds to 28.5% of women worldwide undergoing this delivery modality 8 .
Brazil has the second highest cesarean rate in the world (55.7% in 2018), followed by the Dominican Republic (58.1% in 2018) 8 .Studies presented significant linear upward cesarean rate trends in Brazil from 1994 to 2009 10 , 2000 to 2011 11,12 , 2001 to 2015 13 , and 2014 to 2017 14 .However, Belarmino et al. 15 showed stable cesarean rates at the national and macro-regional levels and a slight decrease in Southeastern Brazil from 2010 to 2017, suggesting the possible existence of inflection points in the historical series of deliveries in Brazil.
Cesarean section is a multifactorial phenomenon positively related to better socioeconomic conditions and/or access to health services [11][12][13] .Data from the National Health Survey 16 conducted from 1990 to 2013 with 16,175 women showed that cesarean sections are more prevalent in Midwest, Southeast, and South regions of the country and among women with higher schooling levels, health insurance, and who were older in the first pregnancy, suggesting the existence of inequalities regarding this delivery modality 16,17 .
For decades, the Brazilian Ministry of Health has been developing public policies aimed at women's health care, such as the Integral Attention to Women's Health Program 18 .The Human-ization of Prenatal And Birth Program 19 and the National Policy for Integral Attention to Women's Health 20 were important milestones for changing practices related to delivery in Brazil and resulted in the Rede Cegonha (Stork Network) program 21 , which aimed to change the model of delivery and birth, encouraging good practices based on scientific evidence, and had reducing unnecessary cesarean sections as one of its goals.The Parto Adequado (Adequate Delivery) program (2015)  for supplementary health and the Parto Cuidadoso (Careful Delivery) program (2018) for the SUS also stand out, aiming to monitor online cesarean deliveries in Brazil, as well as the Apice-On, an improvement and innovation project focused on obstetric and neonatal care and teaching 21 .
Due to its territorial extension and heterogeneity regarding socioeconomic and cultural conditions, adherence to public policies, and access to health services, both the occurrence and evolution of cesarean sections in Brazil may have heterogeneous patterns between the different levels of aggregation in time.Thus, this study aimed to analyze the temporal evolution of cesarean rates in Brazil, its macro-regions, and federative units (FUs), considering possible trend changes over a long period (1994-2019), as well as to estimate the projections of this delivery modality for 2030.

Methods
This was an ecological time-series study on cesarean trends in Brazil.The Guidelines for Accurate and Transparent Health Estimates Reporting (GATHER) was used to build the database, analyze, and present the results of the study 22 .
Data on cesarean sections from 1994 to 2019 were collected from the Information System on Live Births (SINASC), which was made available by the Brazilian Ministry of Health in http://tabnet.datasus.gov.br/cgi/deftohtm.exe?sinasc/cnv/ nvuf.def.
Brazil, its five geographical macro-regions, and 27 federative units were the aggregation levels considered.Cesarean rate (%) was the response variable, obtained by the quotient between the number of cesarean births and the total number of live births in the same year, multiplied by 100.The calendar year was the regressive variable.
For trend analysis, a joinpoint regression model was used to assess the occurrence of possible points of significant changes in the trend.During the modeling strategy, the possibility of adding one or more inflection points to the model was tested.The number of inflections used in the analysis resulted from models defined later to allow the best representation of the trend, with the lowest number of inflection points.Moreover, the slope of the line segment or annual percent change (APC) was estimated with a 95% confidence interval, as well as the variation of the entire period by the average annual percent change (AAPC).The AAPC was estimated as a weighted geometric mean of the APC with weights equal to the length of each line segment during the pre-specified fixed interval.In upward trends, the APC/AAPC and the 95%CI lower limits were higher than zero (positive).In downward trends, the APC/AAPC and the 95%CI upper limits were lower than zero (negative) 23 .Rates with the APC/AAPC equal to zero and/or 95%CI containing zero were considered stationary.Significance tests were performed using the Monte Carlo permutation technique with 4,999 permutations 24 .For each trend found, 95%CI and a 5% significance level were used.Temporal analyses were performed in the Joinpoint Regression Program 25 , and the number of points required for the adjustment of each segment was automatically selected by the standard software configuration.
Cesarean rate projections for 2030 were estimated by autoregressive integrated moving average (ARIMA) models adjusted for the three levels of aggregation adopted.Initially, the assumptions of stationarity and seasonality of data were evaluated.Stationarity was analyzed by autocorrelation function plots and the Dickey-Fuller test increased with a 5% significance level.If the time series was not stationary, a differentiation test was performed.Seasonality was evaluated using a time series and a partial autocorrelation function plot.
In the selection of ARIMA models for each subsample, the lowest values of the second-order Akaike information criterion (AICc) and the Bayesian information criterion (BIC) were considered.Analyses were performed in the R Studio program 26 using the forecast, tseries, and xts packages.
The behavior of cesarean rates from 2020 to 2030 was analyzed using the AAPC, in accordance with Boerma et al. 9 .
The study did not require approval by a Research Ethics Committee, since the aggregated secondary data analyzed were of public domain, with unrestricted access.

Caesarean rate trends
The annual average cesarean rate in Brazil significantly increased by 2.1%, considering the complete series.During this period, we observed four temporal behaviors by segmented modeling: a rapid growth until 1996 (APC=11.4%),followed by a slight decrease until 2000 (APC=-3%), a consequent growth until 2012 (APC=3.6%),and stabilization until the end of the series (APC=0) (Table 1).
Despite the different temporal behaviors, all macro-regions showed a significant increase in cesarean rates in the entire study period.After segmented modeling, North, Northeast, and Midwest regions showed significantly higher percentage increases from 2001 to 2012, followed by smaller increases until the end of the series.In other macro-regions, increases were higher from 1994 to 1996, followed by a significant decrease until 1999 and a subsequent increase until 2012.After this year, rates stabilized in South and Midwest regions and significantly decreased in the South.The highest average percentage increases occurred in Northeast (AAPPC=3.2%)and North (AAPC=2.3%)regions, with average growth proportions above the national variation, considering the entire study period (Table 1).
The number of segments formed for FUs ranged from two (n=3 FUs) to five (n=3 FUs), with a mode equal to four segments (n=9 FUs).
The trends in these segments did not have a defined pattern and despite this heterogeneity, all FUs, except for Mato Grosso, showed a significant upward trend in annual mean cesarean rates from 1994 to 2019.During this period, the largest average annual percentage increases occurred in Amapá (5%), Ceará (4.7%), and Sergipe (4.5%).On the other hand, Mato Grosso do Sul (0.5%), Rio de Janeiro (0.9%), and Goiás (1.1%) had the lowest increases (Table 2 and Figure 1).
In general, FUs in Northern and Northeastern Brazil had the lowest rates at the beginning of the historical series and showed higher upward trends in the 2000s.On the other hand, FUs in other macro-regions, such as Santa Catarina, Paraná, Rio de Janeiro, and Espírito Santo, had high rates at the beginning of the series and from 2012 to 2019, underwent a process of decelera-tion that promoted stabilization or even downward trends (Table 2 and Figure 1).

Analysis of caesarean rate projections
The analysis of projections showed that in 2030, the percentage of cesarean births in Brazil will be 57.4%, with a higher concentration in Southeast and South regions and rates 13% higher than the national estimate (Table 3).FUs in North (Rondônia, Amazonas, and Roraima) and Northeast regions (Rio Grande do Norte, Ceará, and Alagoas) had both the highest projected cesarean rates and the lowest estimates (Table 3 and Figure 1).
When considering the evolution of the projected cesarean rates from 2020 to 2030, the AAPC was positive for Brazil (0.1% per year)  and its macro-regions (below 2%), except for the Midwest region (-0.1%).FUs in Northern and Northeastern Brazil had a positive AAPC, ranging from 0.4% to 3%, except for Amazonas and Alagoas (0% and -0.6%, respectively).On the other hand, FUs in the other macro-regions had AAPC values below and/or close to zero, except for Rio Grande do Sul (1.7%) (Table 3).

Discussion
From 1994 to 2019, cesarean rates were very high compared to the parameters recommended by the WHO 1 and showed a general upward trend in all levels of aggregation adopted.Moreover, both the highest rates of the historical series and the highest projected rates belonged to Midwest,

Caesarean rate variations
In 2019, cesarean rates in Brazil were above the global estimate (21.1%; n=154 countries) and higher compared with countries with the highest rates in the world, such as Cyprus (55.3%),Egypt (51.8%), and Turkey (50.8%).Even countries without high cesarean rates showed upward trends from 1990 to 2018, which represents a worldwide public health problem 8   (1994-2019).it continues cesarean rates, corroborating the results of the National Health Survey from 1990 to 2013 16 .FUs have a pattern of spatial dependence in the distribution of the prevalence of cesarean delivery, with clusters in Southeastern, Southern, and Midwestern Brazil with a high prevalence of cesarean delivery and correlated to higher human development indexes 17 .

Caesarean rate trends
Since the beginning of the monitoring of births in Brazil, cesarean rates have gradually increased by about 30% in the early 1980s, 40% in the early 1990s, 50% in 2009, and 55.7% in 2017 8,27 .Nationally based studies have shown a linear upward cesarean rate trend [10][11][12][13][14] .However, this study showed the formation of inflection points from 1994 to 2019 by segmented regression for the aggregates studied.This model is an efficient and flexible statistical method, capable of establishing inflection points and a cesarean rate trend pattern per aggregation unit in different periods.The behavior of the response variable can be analyzed in different periods of the explanatory variable (time) or separately, relating the trends to the cultural, socioeconomic, and political specificities of each FU.
Brazil and its macro-regions, especially the Southeast, showed successive increases in cesar-  ean rates in the first three years of the historical series (1994-1996).This period follows the implementation of SINASC and the progressive increase in the coverage of this system, which was created in 1990 and until 1998, was already operating in all municipalities of the country 28 .During this period, the hegemonic process of hospitalization and medicalization of the delivery process, which since the 1950s has contributed to the removal of the control of women in giving birth, was improved.
The decrease from 1996 to 1999/2000 may be due to the agreement between the Brazilian Ministry of Health and Health Departments that established a maximum limit for cesarean sections in the SUS, restricting the transfer of resources to this limit.Moreover, the Ministry of Health increased by 160% the amount of compensation for vaginal delivery and established the payment for labor analgesia.Ordinance 2,816/1998 stipulated limits for the payment of caesarean sections to hospitals: 40% for the second half of 1998, expecting a semiannual gradual reduction until reaching 30% in 2000, contributing to a reduction in rates within the SUS and outsourced services 29 .During this period, cesarean rates significantly decreased by 3% in Brazil and its macro-regions, except for the Northeast.From 1999 to 2002, cesarean rates significantly increased in Brazil and its macro-regions, coinciding with the replacement of Ordinance 2,816/1998 by 466/2000, which implemented the National Pact for the Reduction of Cesarean Rates.This document provided for a reduction in the proportion of cesarean sections of 25% by 2008, sharing the responsibility for monitoring hospitals with state administrations 30 .However, only few FUs met its targets and some of them had not meet any target until 2007.Thus, besides the decentralization of actions to the state level, the great contribution of the private sector in the increase in cesarean sections during this period possibly negatively affected cesarean rates in Brazil.On the other hand, we can interpret the stabilization trend from 2012 to 2019 in South and Midwest regions, as well as the decrease in Southeast, due to the policies implemented in the public sector and supplementary health since 2011, such as the Rede Cegonha program, which includes strategies based on the principles of hu- Source: Authors.
manization and proposes the paradigm of a new model of delivery care, from birth and health of children, ensuring the reduction of maternal and neonatal mortality.Moreover, we highlight the Diretrizes de Atenção à Gestante: a operação cesariana (Guidelines for Care for Pregnant Women: cesarean section) 31 and the Parto Cuidadoso initiative of the Ministry of Health, which is an online system to monitor the amount of cesarean sections performed in SUS 32 .
In the field of supplementary health, the Parto Adequado program (2016) of the National Health Agency (ANS) presents important results among the participating hospitals.Cesarean rates in health plan operators decreased from 84.5% in 2013 and to 82.7% in 2020 (-1.8%).Moreover, from 2017 to 2019, the percentage of vaginal deliveries increased from 33% to 37% in the participating hospitals.Neonatal ICU admissions decreased by 18%, from 40 per 1,000 live births to 33 per 1,000 live births, and about 20,000 unnecessary cesarean sections were avoided 33 .
Thus, actions and policies aimed at the humanization of childbirth cause their effects in a discrete but cumulative way and are only part of the causal chain involved in the trend of the type of delivery, besides social, economic, cultural, and demographic factors.
Regarding differences in regional trends, the richest macro-regions of Brazil presented significant increases at the beginning of the series and since 2012, cesarean rates stabilized or decreased.According to scientific evidence, Brazilian women with a higher socioeconomic status, living in FUs with higher gross domestic product (GDP) and human development index (HDI), undergo more normal delivery.On the other hand, women with a lower socioeconomic status, living in poorer FUs, still undergo more cesarean section, which is sometimes seen as a consumer good.This evidence is found in FUs in Southeastern Brazil, which had the highest GDP in the country in 2017 and where the variables higher maternal schooling level and higher prenatal coverage were associated with a reduction in cesarean rates 15 .
The result of a review of studies conducted in Southeastern and Southern Brazil on models of delivery care is also important when considering regional differences.Results showed that the use of new delivery care practices in line with the guidelines of the Ministry of Health, such as delivery care performed by multidisciplinary teams, including obstetric nurses, using complementary integrative humanized therapies in the pregnancy period, delivery in normal delivery centers, encouraging the participation of companions, offering non-pharmacological measures for pain relief, and care for prepartum, childbirth, and postpartum in a single environment, have contributed to the reduction of unnecessary cesarean sections 34 .
All FUs had cesarean rates higher than 30% since 2012.This value has been considered the upper limit of the adjusted reference rate for the Brazilian population, according to the C-Model tool, developed by the WHO 31 .Therefore, many of these sections were unnecessary and would not be related to improvements in maternal and neonatal mortality at the population level 1 .
Differences in trends in FUs may show the length of the different time periods used, as well as differences in the modeling strategies adopted.In general, the strategy adopted in the aforementioned studies uses a priori one time interval and finds estimates to interpret the trend for this period.In this study, we considered the entire period with available information on the delivery modality and obtained from the modeling by inflection points cesarean rate trends segmented later.Thus, this study presents more detailed trends and trend changes over an extended period.Moreover, the processes of demographic and epidemiological transition and the implementation and effectiveness of health policies in each FU should be considered 35 .
Except for Mato Grosso, FUs showed a significant increase in cesarean rates in the complete series, but different trend patterns in the segments formed by different inflection points.We observed two temporal patterns: FUs that had the lowest cesarean rates at the beginning of the series and showed a rapid increase from the 2000s and FUs that had high rates at the beginning of the series and underwent a process of deceleration that promoted stabilization or even downward trends since 2012.This finding shows the different moments of FUs in relation to obstetric transition 36 , which has the secular tendency to move from a pattern of high maternal mortality to low maternal mortality, from the predominance of direct obstetric causes of maternal mortality to an increasing proportion of indirect causes associated with chronic-degenerative diseases, the aging of mothers, and the modification of the natural history of pregnancy and delivery to a pattern of institutionalization of care, increased rates of obstetric intervention, and eventual over-medicalization.
These differences present the phenomenon of the "two-stage growth" of the cesarean epidemic in Brazil.This phenomenon already affects other countries, such as China, where cesarean rates increased rapidly in large and supercities in the 1990s and early 2000s, but decreased in the last ten years, while cesarean rates in rural areas steadily increased 37 .Thus, cesarean sections should be conducted in a sustainable way, considering each epidemiological, technological, and social factor, the context of implementation of public policies, and the respective scenarios projected for the upcoming decades.

Analysis of caesarean rate projections
After 2019, cesarean rates in Brazil will increase slightly (0.1% per year), remaining at a high level until 2030 and representing more than half of deliveries in the country.This slow growth corroborates Belarmino et al. 15 , who hypothesized that Brazil reached a plateau in the prevalence of cesarean section (60%) and projected reduced rates from 2017.Despite signs of stabilization, in 2030, the cesarean rate in Brazil is expected to be 2.7 times higher than the global average 8 and Southeast and South regions, as well as the states of Rondônia, Ceará, Rio Grande do Norte, Piauí, and Rio Grande do Sul, will have cesarean rates higher than 70%.Thus, the persistence of high cesarean rates in Brazil requires the adoption of effective and more articulated policies, capable of reducing the number of cesarean sections, combined with movements to raise awareness of women about the advantages of vaginal delivery based on scientific evidence, while still considering their autonomy to choose the delivery modality.
Macro-regions with the best socioeconomic indicators will have higher cesarean rates in 2030; however, considering only 2020 and 2030, most FUs in macro-regions with the highest cesarean rates (Southeast and South regions) will have stable or reduced rates (except for Rio Grande do Sul) in the average annual percent change, whereas in FUs in North and Northeast regions, the projections show percentage increase (except for Amazonas and Alagoas).Moreover, in Midwest, all FUs presented a negative average annual percent change, except for the Federal District.The pattern of temporal distribution found supports the hypothesis of a two-speed epidemic within Brazil, in which aggregation units with a high cesarean rate at the beginning of the series would tend to stabilize or decrease from 2012.
The methodology used for prediction consider past cesarean rates as the greatest predictors for future projections, thus, the detailed analysis of trends in the historical series helps understand the different behaviors expected for 2020 to 2030.Alagoas, for example, already showed signs of decrease since 2012, with successively decreasing rates, which directly affects the projections for 2030.On the other hand, Amazonas shows signs of stabilization since 2010 and the projections confirmed this trend.The projected rate for Rondônia in 2030 is the largest in Brazil.This FU is part of the group with very high rates at the beginning of the series and in 2019, it had the second highest rate in the country (66.7%).We already expected these projections, especially considering that from 2020 to 2030, its annual percentage change is positive (1.6%), one of the largest in Brazil.Moreover, 2020 and preliminary 2021 data already show this increase.However, most extreme projections at the end of the series may present a higher degree of inaccuracy.

Strengths and limitations
This study analyzed an extensive series of information on cesarean sections and identified general and later segmented trends (from inflection points).We used data to project rates for Brazil in 2030 by autoregressive integrated moving average models.These models are able to detect trend changes in the historical series and predict the behavior of the response variable.General estimates and at broader aggregation levels can hide differences and inequalities within a country and, thus, the use of hierarchically lower levels of aggregation produces more specific information for each context of implementation of cesarean monitoring actions.The trend estimates obtained in this study are robust, but conditioned to the coverage of SINASC in FUs, which was wide, homogeneous, and higher than 90%, except for Maranhão (84.3%) and Bahia (88.5%) 28 .On the other hand, these estimates come from secondary data, which have limited information on, for example, the source of funding and the clinical indication of the surgery.The inclusion of only live births was another limiting factor.In the case of projections, we did not considered the possible effects of the COVID-19 pandemic 8 on both cesarean sections in Brazil and draft laws already approved in São Paulo (2019), Pará (2020), and Paraná (2020) or being discussed in the Chamber of Deputies and Senate since 2021, which guarantee to pregnant women the right to choose for cesarean section in the SUS and would negatively affect the advances made so far.

Final considerations
We observed high cesarean rates and varied time patterns of increase, stabilization, or decrease in the aggregation units analyzed.Brazil had a trend of stabilization since 2012; however, projections show high values for some regions and FUs until 2030.Inflection points show the heterogeneity of the phenomenon in time and contribute to a better historical understanding.The use of models with inflection points, along with projection methods, is effective to identify priority interven-tion units in time, supporting decision making, the implementation of strategies of the sectors involved, and a more incisive action regarding the excessive and/or unnecessary performance of cesarean sections.Thus, the humanization of childbirth would assume a priority role in the current agenda of health actions in Brazil by strengthening and improving the existing and others specific initiatives for each context, reducing the number of cesarean sections and, consequently, maternal and perinatal mortality, to achieve the target of the Sustainable Development Goals for 2030.
After this period, North and Northeast regions showed a significant upward trend and the other macro-regions, stability (Midwest) or decrease (South and Southeast), corroborating the hypothesis of heterogeneity of temporal patterns.

Table 2 .
Cesarean rate trends (%) in Brazilian federative units . Nationally, Midwestern, Southern, and Southeastern Brazil remain with the highest

Table 3 .
Projections of cesarean rates (%) in Brazil, it macro-regions, and federative units (2020, 2025, and 2030) and characteristics of the selected models.