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Conteúdo (article):

COSTS AND CHARACTERISTICS OF ADMISSIONS DUE TO AMBULATORY CARE-SENSITIVE CONDITIONS IN CHILDREN UNDER ONE YEAR OF AGE IN SÃO PAULO

Lays Janaina Prazeres Marques1.
E-mail: laysjpmarques@gmail.com ORCID: https://orcid.org/0000-0003-4511-4995

Antonio Carlos Pereira2.
E-mail: apereira@fop.unicamp.br ORCID: https://orcid.org/0000-0003-1703-8171

Augusto Cesar Sousa Raimundo3.
E-mail: augustocesarsr@gmail.com ORCID: https://orcid.org/0000-0001-7736-9189

1Departamento de Epidemiologia. Faculdade de Saúde Pública, Universidade de São Paulo. São Paulo – SP, Brasil.
2,3Departamento de Odontologia Social. Faculdade de Odontologia de Piracicaba, Universidade Estadual de Campinas. Campinas – SP, Brasil.

Correspondence: Lays J P Marques. Departamento de Epidemiologia - Faculdade de Saúde Pública da Universidade de São Paulo. Av. Dr. Arnaldo, 715 - Cerqueira César. Zip code: 01246-904. São Paulo – SP, Brasil. E-mail: laysjpmarques@gmail.com

ABSTRACT
This research aimed to estimate the direct costs and analyze the epidemiological aspects of ambulatory care-sensitive conditions (ACSC) in children under one year of age, São Paulo municipality, 2011-2022. Total and average costs were calculated according to ACSC diagnosis groups by components (early neonatal, late neonatal, and post-neonatal). The trend in ACSC rates was analyzed using the Prais-Winsten generalized linear regression. 98,679 hospitalizations were identified. There was an annual increase of 10.2% (95%CI:7.70;12.68) in the ACSC rate of early neonates and in the other components the trend was stationary. The cost for the period was estimated at R$130.5 million in <1 year, a reduction of 8.6%. The highest absolute values were related to the most frequent causes, such as lung diseases with 43.7% of the cost in <1 year, 52.5% in late neonates, and 48.8% in post-neonates. In early neonates, 83.5% of the cost was attributed to prenatal-related diseases, especially congenital syphilis. It is concluded that it was possible to identify the costs and characteristics of hospitalizations, showing an increase in ACSC rates and the conditions that require greater attention from primary health care services to reduce hospitalizations and hospital costs in the public sector.

Keywords: Primary Health Care, Maternal and Child Health, Hospital Costs.

INTRODUCTION
Admissions due to ambulatory care-sensitive conditions (ACSC) represent a set of potentially avoidable diagnoses to the extent that Primary Health Care (PHC) actions are timely and resolving. Thus, ACSC represents an indirect measure of access and quality of care provided by the Family Health Strategy (FHS) in PHC1. Monitoring this indicator is essential to support strategies to prevent unnecessary hospitalizations, optimize the use of beds, and consequently reduce healthcare costs2.
Primary Health Care actions can contribute to solving around 80% of the population’s health needs3. It is believed that hospitalizations resulting from conditions subject to early detection by the first level of health care reflect deficiencies in PHC coverage and effectiveness. When actions at the first level of care are offered appropriately and on time, they can help reduce the risk of worsening clinical conditions and the subsequent need for hospitalization1,4,5.
Several Brazilian studies have shown that the child population has the highest proportion of ACSCs in the country6. Unlike the profile of adults, in childhood ACSCs are represented, above all, by acute conditions3. In recent decades, respiratory, infectious/parasitic diseases and those originating in the perinatal period have represented the main causes of ACSC in children in Brazil2,6. However, there are regional differences in the prevalence of ACSC in children under one year of age, where gastroenteritis prevails in the North and Northeast, and in the South, Southeast, and Central-West, respiratory diseases are more frequent6-9. These differences can be attributed to socioeconomic conditions (basic sanitation, education, income), climate influence, the available health service network, and the work of the FHS teams10.
In addition to the consequences of hospital admission on health conditions, which can increase the risk of death and sequelae, ACSCs in children under one year of age also cause a high financial impact, resulting in increased expenses for the financial management of the Unified Health System (Sistema Único de Saúde - SUS) in Brazil. Given the context of SUS underfunding, measuring the costs resulting from avoidable hospitalizations becomes essential for better allocation of resources and setting priorities11.
Despite the growing number of studies related to ACSC in childhood, there is still little research on the costs by diagnostic groups in children under one year of age and their subcomponents (early neonatal, late neonatal, and post-neonatal), especially at the municipal level. Therefore, this study aimed to estimate direct costs and analyze the epidemiological aspects of admissions due to ambulatory care-sensitive conditions (ACSC) in children under one year of age in the city of São Paulo between 2011 and 2022.

METHODS
Study area
The study area refers to the municipality of São Paulo (MSP), capital of the State of São Paulo, located in the Southeast region of the country. MSP represents the largest urban center in Latin America, with around 12 million inhabitants distributed over a territorial extension of 1,521,110 km². The average per capita income is 4.2 minimum wage (USD 865.38), and the Human Development Index (HDI) is 0.80512.

Study definitions
All admissions due to ambulatory care-sensitive conditions of children under one year of age were included. The set of ACSC causes took as a reference the 19 groups of diseases, with 74 diagnoses classified according to the 10th International Classification of Diseases and Related Health Problems (ICD-10), published in ordinance no 221 of the Ministry of Health, on April 17, 2008, which defined the Brazilian list of ambulatory care-sensitive conditions13.

Data Sources
The data corresponding to hospitalizations were obtained from the Hospital Information System (Sistema de Informações Hospitalares - SIH), made available by the Information Technology Department of the Unified Health System (DATASUS). To compose the denominator of ACSC rates, the total number of live births obtained through the Live Birth Information System (Sistema de Informações sobre Nascidos vivos - Sinasc), made available by the city hall of São Paulo municipality (https://www.prefeitura.sp.gov.br/cidade/secretarias/saude/tabnet/) was used. Information regarding the supplementary health insurance coverage rate was obtained through the ANS TabNet (http://www.ans.gov.br/anstabnet/), while data on the primary health care coverage rate was obtained from the e-Gestor website (https://egestorab.saude.gov.br/).

Cost Analysis
This is a cost-of-illness study (burden of disease) of the top-down type (macro-costing), from the perspective of a public agency providing health services, which reflects the cost spent by the final payer (SUS) in the form of reimbursement. The direct medical and hospital admissions costs due to ACSC in the city of São Paulo were estimated. In this study, indirect and intangible costs were not considered. The time horizon of the study corresponded to 12 years (January 1, 2011 to December 12, 2022).
A partial economic analysis was carried out, where direct medical and hospital costs were evaluated, with information extracted from payment records from the hospital admission authorization, an instrument where care resulting from hospitalizations financed by the SUS is recorded. The total and average cost of hospital admission authorization was analyzed according to diagnostic groups for all age components. The average cost was calculated as the quotient of the total cost of hospital admission authorization divided by the total number of hospitalizations according to age components and was also stratified by diagnostic groups.
Information on the national reference payment values defined by the Ministry of Health for remuneration for procedures is described in the Procedures, Medications and Orthosis Prosthesis and Special Material Table Management System (SIGTAP) of the SUS. For temporal adjustment purposes, the values for the period were adjusted for inflation using the period from January 2011 to December 2021 as a basis, according to the Extended National Consumer Price Index (IPCA). Monetary values were presented in real currency (R$).

Epidemiological analysis
The ecological approach of the study included the following epidemiological aspects: calculation of the temporal trend in the ACSC rate; analysis of the correlation between the ACSC rate and primary health care and supplementary health insurance coverage rates; and characterization of hospitalizations according to covariates.
Admission rates by ACSC were calculated using the total number of hospitalizations of children under one year of age and its age subcomponents as the numerator, and the number of live births as the denominator. Hospitalizations for children under one year of age were considered to be those that occurred in children aged less than 11 months and 30 days, that is, 364 days from hospital admission. The age subcomponents were divided into three periods, corresponding to early neonatal (0 to 6 days of life), late neonatal (7 to 27 days of life), and post-neonatal (28 to 364 days of life).
Additionally, the correlation between ACSC rates in children under one year of age with PHC and supplementary Health insurance coverage rates (in children under one year of age) was investigated. The Shapiro-Wilk test was applied to verify the assumption of normality of the variables, followed by the Pearson correlation test, with a significance level of 5% (p<0.05).
In the time series analysis of ACSC rates, Prais-Winsten generalized linear regression was used, which allows the first-order serial autocorrelation to be corrected. Models for the ACSC rate in children under one year of age and its age subcomponents were analyzed. The adjustment line between the points of the series whose trend was intended to be estimated was defined by the equation y = β0 + β1x, where, y is the ACSC rate (dependent variable); x is the year of hospitalization (independent variable); It is β is the regression coefficient. The data modeling process included the base 10 logarithmic transformation of the y values, to reduce the heterogeneity of the variances of the analysis residues. The presence of serial autocorrelation was assessed using the Durbin -Watson statistic. Estimates of the annual percentage change (APC) were calculated using the equation: APC = [-1+10^(β1)]∙100. The respective 95% confidence intervals will be obtained by: 95%CI = [-1+10^(β1minimum)]∙100;[-1+10^(β1maximum)]∙100. It was verified whether the behavior of the series was stationary (p≥0,05), decreasing (p<0.05 and negative β1), or increasing (p<0.05 and positive β1). The p values were obtained using the Wald test at a significance level of 5%14.
The characterization of hospitalizations was carried out based on the following variables: mean and median length of hospital stay (days); sex (male, female); race/ ethnicity (white, non-white, unknown); progression to death (yes, no); nature of hospitalization (elective, urgent); and diagnostic groups defined by the Brazilian ACSC list. Descriptive statistics were applied with the distribution of absolute and relative frequencies and the calculation of the mean and median. Data were tabulated and analyzed using Microsoft Excel® and R software (The R Project for Statistical Computing).

Ethical considerations
This study complied with the ethical precepts of the resolution of the National Health Council no 510/16, which provides for the exemption from ethical approval for research using information in the public domain.

RESULTS
From 2011 to 2022, there were 98,679 hospitalizations for ACSC in children under one year of age in São Paulo municipality, with an increase of 4.7% between the first (n = 8,748) and the last year (n = 9,160). Hospitalizations due to ACSC represented 22.8% of total hospitalizations (n = 433,292) in the first year of life. Regarding representation by age component, it was found that 7.5% (n = 7,419) of hospitalizations for ACSCs corresponded to the early neonatal period, 5.0% (n = 4,959) to the late neonatal period, and 87.5% (n = 86,301) to post-neonatal.
In the temporal evolution of ACSC rates, a sharp decline was observed in 2020 among children under one year of age, especially in the post-neonatal component, as opposed to an increase that occurred in the early neonatal component. This period is marked by the beginning of the Covid-19 pandemic in Brazil. The correlation test between the ACSC rate in children under one year of age and the primary health care coverage rate was r= -0.54 (p = 0.07; 95% CI: -0.85;0.05), and between ACSC rate in children under one year of age, and supplementary health insurance coverage rate was r= -0.38 (p = 0.22; 95% CI: -0.78;0.25), showing a negative correlation and absence of statistical significance in both cases (Figure 1).
Figure 1

The ACSC rate (per thousand live births) in children under one year of age went from 49.6 in 2011 to 69.4 in 2022, corresponding to a variation of 1.8% per year (95% CI: -1, 54;5,26). For the early neonatal component, ACSC rates showed an annual increase of 10.2% (95%CI: 7.70;12.68), varying from 2.6 to 6.4 per thousand live births. Among late neonates, there was a stationary trend with a variation of 0.3% (95%CI: -3.46;4.29) per year and rates fluctuating from 2.7 to 3.3 per thousand live births. The trend in rates among post-neonates was also stationary, with an annual variation of 1.0% (95%CI: -2.88;5.10), changing from 44.2 to 59.7 per thousand live births between the first and the last year of the series (Table 1).
Table 1

Regarding the total number of hospitalizations, it was found that the average length of hospital stay decreased with the increase in the age of the newborn, being higher among early neonatal components (10.8 days) and shorter among post-neonatal (5.2 days). The male sex was predominant in almost all age groups, except for early neonatal, in which 51.0% of hospitalizations were represented by females. White race/ethnicity constituted the majority of hospitalizations in children under one year of age and subcomponents, except early neonatal, which accounted for 31.4% of hospitalizations in non-whites. However, the high percentage of unfilled fields for this information draws attention, being higher among early neonates. Regarding the nature of the hospitalization, the majority were urgent, with a higher percentage of hospitalizations in the post-neonatal component (97.5%) compared to the others. The occurrence of death due to ACSC was more frequent in hospitalizations of early neonates (0.5%) (Table 2).
Regarding the causes of ACSC, lung diseases represented the main cause, both for children under one year of age (52.7%), and for late neonates (53.7%) and post-neonates (57.1%). This was followed by kidney and urinary tract infections, which accounted for 15.0% for the late neonatal component, 9.1% for the post-neonatal component, and 8.9% for those under one year of age. Thirdly, infection of the skin and subcutaneous tissue represented 8.2% for late neonates, and infectious gastroenteritis and complications represented 8.8% and 8.0% for post-neonates and children under one year of age, respectively. In the early neonatal component, diseases related to prenatal care and childbirth, represented mainly by congenital syphilis, were responsible for 86.0% of hospitalizations, followed by diseases preventable by immunization and sensitive conditions with 3.3% and kidney infections and urinary tract with 2.3% (Table 2).
Table 2

The total cost of hospitalizations for children under one year of age was estimated at 130.5 million reais, with 14.7 million (11.3%) attributed to the early neonatal component, 8.9 million (6.9%) to the late neonatal and 106.7 million (81.8%) post-neonatal. Despite the amount observed being high, comparing the year 2011 with 2022, there was a decrease of 8.6% in the total cost of children under one year of age, with a more significant reduction in the late neonatal component (-19.1%), followed by post-neonatal (-14.3%). However, the early neonatal component showed an increase of 66.4%. In addition to the total cost, the average expenditure on these hospitalizations decreased by 12.7% among children under one year of age, going from R$1,188.9, at the beginning of the series, to R$1,037.7, in the last year of study. The early neonatal, late neonatal and post-neonatal components also showed a reduction in the average cost between the beginning and end of the period, with -8.3%, -10.9%, and -15.1% respectively (Figure 2).
Figure 2

The average cost in the period was R$1,322.6 for children under one year of age, being higher among early neonates (R$1,987.1), followed by late neonates (R$1,814.8) and post-neonates (R$1,237.2). In the diagnostic groups, it was found that heart failure was the cause of the highest average cost both for children under one year of age (R$10,434.1) and for the late neonatal (R$9,258.1) and post-neonatal components. (R$11,099.1). For the early neonatal component, the highest average cost was observed for inflammatory disease of the female pelvic organs (R$8,504.5). Regarding total costs, lung diseases represented the group of causes with the highest costs among children under one year of age (R$57.0 million; 43.7%), late neonates (R$4.7 million; 52.5%), and post-neonates (R$52.2 million; 48.8%). Among early neonates, diseases related to prenatal care and childbirth represented 83.5% of the cost (R$12.3 million) (Table 3).
Table 3

DISCUSSION
In the São Paulo municipality, the majority of ACSCs occurred in children in the post-neonatal period. ACSC rates increased in all subcomponents although with a significant trend only in early neonates. The Covid-19 pandemic resulted in a sharp reduction in ACSC rates, especially in the post-neonatal component. The most frequent ACSC diagnostic groups were lung diseases in almost all components, except early neonatal, in which Diseases related to prenatal care and childbirth predominated, mostly represented by congenital syphilis. Comparing the first and last years of the period, there was a reduction in total and average spending on ACSC. However, early neonates showed an increase in cost, especially in the diseases group related to prenatal care and childbirth, in which the proportion of the total cost quadrupled between 2011 and 2022.
The results of this study corroborate previous Brazilian research, which demonstrated that the majority of admissions due to ambulatory care-sensitive conditions occur in the post-neonatal component8,15. This fact can be attributed to the difficulties in scheduling childcare appointments, the long wait for care, the conditioning of families to undergo exams and private consultations, even without sufficient financial conditions, and the lack of communication and information during promotion actions for health and continuity of care16.
Unlike what was observed in other Brazilian municipalities, which demonstrated reductions in ACSC rates in children6-9, São Paulo municipality showed an increase in ACSC rates in children under one year of age and subcomponents, with a significant trend only for the early neonatal component. The differences in the aspects of these hospitalizations result from the association of several factors, such as population growth in the age group under one year of age, socioeconomic characteristics, epidemiological conditions, operationalization of health services, and other specificities, inherent to each location10.
There was a sharp reduction in ACSC rates in 2020, especially in the post-neonatal component. During this period, non-pharmacological interventions were proposed to confront the Covid-19 epidemic in Brazil17, such as circulation restrictions imposed by lockdown measures, the mandatory use of masks, and encouraging the adoption of hand disinfection habits. These measures may have contributed to reducing the spread of diseases prevalent in children in this age group, especially lung diseases18,19. On the other hand, children in the early neonatal period had an increase in ACSCs. This fact is due to the impact that response measures to the Covid-19 pandemic had on maternal and neonatal health services in Brazil and around the world20. During this period, there was a restructuring of hospital and maternity services to meet the demand of patients affected by SARS-CoV-2, which reflected in access and quality of prenatal care and childbirth21. In addition, there is the increasing dissemination of misinformation about the consequences of the disease, which has caused fear in using health services, and complications from Covid-19 infections in pregnant and postpartum women22.
ACSC rates in children under one year of age showed a negative correlation with primary health care and supplementary health insurance coverage rates, indicating that one rate tends to decrease when the other increases. The absence of statistical significance found in this study probably indicates that both coverage rates were not sufficient to impact ACSC23. Although the relationship between increased primary health care coverage and reduced ACSC rates is recognized24,25, some research has also not shown an association26,27. One hypothesis is that the impact of expanding primary health care coverage in ACSC would not be immediate and would occur in the medium to long term25. On the other hand, some studies suggest that there may be a threshold at which this association can be established28. Regarding the coverage of supplementary health insurance, its increase could lead to a diversion of hospitalizations to the private health network and a consequent reduction in ACSC rates26. Therefore this, analysis is particularly important within the scope of this study, as the State of São Paulo has the highest percentage of hospitalizations covered by supplementary health insurance at the national level29.
Concerning the length of hospital stay, it was found that the average number of days of hospitalization decreased with the increase in the child\'s age at hospital admission, being higher in early neonates and lower in post-neonates. Furthermore, there was a higher frequency of deaths due to ACSC in the early neonatal component. The neonatal period represents a critical period for the survival of the newborn, and it is estimated that up to 70% of infant deaths occur during this period30. A study carried out with neonates admitted to SUS hospitals in the São Paulo municipality demonstrated a higher concentration of deaths in the first days of life. Contributing factors to increased hospitalization time and risk of death among neonates were identified as low birth weight, prematurity, and low Apgar scores at birth, in addition to a history of maternal complications during pregnancy31.
Regarding the characteristics of hospitalizations, children admitted due to ambulatory care-sensitive conditions were predominantly male in most age groups. Previous studies carried out in Brazil also identified a higher prevalence of hospitalizations among male children32-34. There is evidence that both morbidity and the use of health services are higher in males up to 10 years of age in urban and rural areas35.
White race/ethnicity was more frequent in hospitalizations in almost all age groups. Although the race/color variable was included in the SIH/SUS in 200836, rare studies proposed carrying out an ethnic-racial analysis, especially focused on ACSC in the children\'s segment. Research that evaluated ethnic-racial inequities in hospitalizations for preventable causes in children under five years of age in Brazil between 2009-2014, found 37.9% incompleteness of the race/color variable in the period. Hospitalizations in white children under one year of age increased from 48.6% in the 2009-2011 period to 51.4% in 2012-201436.
The majority of hospitalizations were urgent in children under one year of age and subcomponents. Inadequate demand for hospitals, emergency rooms, and emergency care units (Unidades de Pronto Atendimento - UPA) due to health problems that could be resolved within the scope of primary health care and, therefore, do not fit into these categories, may be related to factors such as resolution, quality, specificity for caring for children, ease of access, experiences and recommendations37. In addition to these, they can be added to the availability of greater resources, such as consultations, laboratory tests, medicines, and imaging tests, sometimes unavailable at the Basic Health Unit (Unidade Básica de Saúde - UBS)38.
Regarding expenses with admissions due to ACSC, a reduction in total and average costs was observed between 2011 and 2022 in children under one year of age and subcomponents. The reduction in total cost was greater in the late neonatal component, followed by the post-neonatal component, as opposed to the increase in the early neonatal component. Dias et al. (2022) found the State of Minas Gerais between 2014 and 2019 the amounts spent on ACSC suffered a reduction in all age groups, except for children under one year of age. On the other hand, a study that analyzed the trend in ACSC spending on children under five years of age in Bahia found a 50.4% reduction in total spending, comparing 2000 and 2012. This was due to the 24.7% decline in the ACSC rate in period39.
In Brazil, the main causes of hospitalizations in childhood are due to primary health care-sensitive conditions40. Extremes of age are recognized as the main factors related to ACSC and also reveal the highest costs when compared to other age groups41. It should also be noted that the medical costs referred to in the present study refer only to direct hospitalization costs, not reflecting indirect and intangible costs associated with early death, social and psychological impact, and adverse outcomes throughout life, including developmental changes and chronic health disorders42,43.
Lung diseases represented the most frequent cause, accounting for more than half of the total number of hospitalizations, and with higher expenses accumulated in the period among late neonates, post-neonates, and children under one year of age. This result corroborates what was observed by Lôbo et al. (2019) in the State of São Paulo between 2008 and 2014, in which lung diseases represented the main causes of ACSC in these components, being responsible for 36.7%, 39.7% and 37.7% of hospitalizations, respectively. However, in the São Paulo municipality, this proportion was higher than the state level. The high costs of lung diseases are confirmed by previous studies, which identified a 62.5% increase in the proportion of costs for hospitalizations of children under 4 years of age, between 2000 and 2013, in Brazil41. It is known that respiratory diseases are prevalent conditions in childhood, due to their greater susceptibility and/or ease of dissemination. These should be identified and treated at the first level of care, without the need for hospitalization, in most cases, if there is resolution in primary health care40.
Infectious gastroenteritis and complications were among the most frequent ACSC diagnoses in the group of children under one year of age. In terms of costs, these were more relevant for the post-neonatal and late neonatal components. National research identified a reduction in infectious gastroenteritis and complications in the participation in ACSC spending in all age groups in Brazil, with the representation of the cost in childhood (≤4 years of age) decreasing from 9.0% in 2000 to 2.9% in 2013. A previous study found a reduction of 31.2% in hospitalizations for gastroenteritis in post-neonates in the State of São Paulo between 2008 and 2014, attributing this reduction to the improvement in sanitation conditions and access to potable water and the growth of the primary healthcare network in the State7.
Among early neonates, the groups of diseases related to prenatal care and childbirth represented the predominant causes in terms of frequency and greater volumes spent in the period. It is noteworthy that 85.7% of total hospitalizations in this component were represented by congenital syphilis. Then, in the group of diseases preventable by immunization and sensitive conditions, it was observed that 94.3% were related to other forms of syphilis (early, late, or unspecified). This finding is similar to that of research that found that congenital syphilis represented 91.2% of all hospitalizations in the group of Diseases related to prenatal care and childbirth in children under one year of age in Brazil8. However, in the São Paulo municipality, the frequency of hospitalizations for congenital syphilis in early neonates was almost three times higher than that found in neonates (29.5%) with up to 27 days of life at the national level between 2000 and 20158. Research that analyzed the direct medical and hospital costs of hospitalizations in the SUS for congenital syphilis in children under one year of age in the State of Ceará, identified an increase of 36.4% in hospital admission authorization (AIH) approved in the period from 2012 to 201744. Maternal syphilis screening through Carrying out rapid tests during prenatal care represents the most cost-effective action to reduce negative pregnancy outcomes, such as low birth weight, prematurity, spontaneous abortion, and neonatal and fetal deaths45.
The highest cause-specific average costs were linked to heart failure diagnoses both for children under one year of age and for the late neonatal and post-neonatal components. Among early neonates, the costs of this cause ranked 3rd. In addition to multiple surgical procedures, these newborns also experience an increase in the length of stay in the intensive care unit (ICU)46. Consequently, they experience greater resource consumption, reflecting an increase in costs disbursed by the SUS.
As it is an ecological study, carried out with secondary data from different data sources, this research is subject to limitations, such as under-registration, incompleteness, and possible problems of diagnostic definition based on the ICD-10 codes of hospitalizations registered at hospital admission authorization (AIH). Furthermore, this approach used only hospitalizations carried out within the scope of the SUS, partially portraying the reality of hospitalizations in São Paulo municipality. It is noteworthy that it was not possible to analyze information considered relevant to the context of ACSC in children under one year of age, such as prenatal care and its adequacy.
This research identified the predominant diagnostic groups of ACSC in children under one year of age and subcomponents. It was observed that more than half of hospitalizations in the late neonatal period, post-neonatal period, and in children under one year of age occurred due to lung diseases, resulting in the highest amounts spent in the period. Among early neonates, diseases related to prenatal care and childbirth were relevant in hospitalizations and hospitalization costs. Congenital syphilis was the protagonist in this scenario, drawing attention to the inadequate provision of prenatal care in the São Paulo municipality. The share of this cause in ACSC spending has quadrupled in the last 12 years. The incidence of children with this disease and its subsequent costs could have been avoided, as well as other causes of ACSC if primary healthcare actions had been timely and persistent. It is noteworthy that studies on the costs of ACSC in children under one year of age are still scarce in Brazil, therefore, more research should be encouraged to understand the temporal evolution and application of these resources according to groups of causes.

COLLABORATORS
LJP Marques participated in the conception, data analysis, interpretation and discussion of results, writing, and final manuscript review. ACS Raimundo participated in the conception, analysis, and interpretation of data and relevant critical review of the intellectual content of the manuscript. AC Pereira participated in the appropriate critical review of the manuscript\'s intellectual content.

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