Detection of gestational and congenital syphilis in Paraná state, Brazil, 2007-2021: a time series analysis

Abstract Objective: To describe temporal trends in the detection rates of gestational and congenital syphilis, by maternal age and health macro-region of the state of Paraná, Brazil, 2007-2021. Methods: This was a time-series study using surveillance data; the trend analysis was performed by means of joinpoint regression, and average annual percent change (AAPC) and 95% confidence intervals (95%CI) were estimated. Results: An increase in statewide detection of gestational syphilis (AAPC = 21.7; 95%CI 17.7; 32.8) and congenital syphilis (AAPC = 14.8; 95%CI 13.0; 19.7) was found; an increase was also found in the health macro-regions, with the Northwest (gestational, AAPC = 26.1; 95%CI 23.4; 31.6) and North (congenital, AAPC = 23.8; 95%CI 18.8; 48.9) macro-regions standing out; statewide rising trends were observed for young women [gestational, AAPC = 26.2 (95%CI 22.4; 40.6); congenital, AAPC = 19.4 (95%CI 17.6; 21.8)] and adult women [gestational, AAPC = 21.3 (95%CI 16.9; 31.9); congenital, AAPC = 13.7 (95%CI 11.9; 19.3)]. Conclusion: Maternal and child syphilis detection rates increased in the state, regardless of maternal age and health macro-region.


INTRODUCTION
Syphilis, a sexually transmitted infection, remains a challenge for public health policies in Brazil due to its gestational and congenital forms, which account for a significant portion of infection cases recorded nationally. 1,2For example, the Ministry of Health reported 74,095 cases of syphilis among pregnant women and 27,019 among children in 2021 nationwide; in the state of Paraná, especially, 3,223 cases of the infection among pregnant women and 868 among children, were recorded, in the same period. 35][6] In addition, maternal sociodemographic and behavioral characteristics, such as inconsistent condom use, low monthly income, history of sexually transmitted infection substance use, and aged 35 years and older, are described as predictors of gestational and congenital syphilis. 4,5,7,8 Paraná, the main challenges for the control of maternal and child syphilis are related to women aged 20 to 39 years and with low level of education, whose sexual partners are not treated 9 -possibly due to weaknesses in prenatal care. 10In 2023, the state received the "bronze seal" of practices towards the elimination of mother-to-child transmission of syphilis, 11 primarily following the implementation of the Paraná's Mother Network in 2012, aiming at the early detection and linkage of pregnant women to prenatal care. 12king into consideration that maternal characteristics, such as age, and contextual factors, such as place of residence and healthcare access, are relevant to epidemiology and can be considered in monitoring syphilis indicators -especially when targeting the elimination of mother-to-child transmission -this study aimed to describe temporal trends in the detection rates of gestational and congenital syphilis, by maternal age group and health macro-region of the state of Paraná, Brazil, between 2007 and 2021.

Study design and ethical aspects
This time-series study involve the use of aggregated data organized over time, regarding the annual detection rates of gestational and congenital syphilis in the state of Paraná.Given that this study design included aggregate and anonymized data, the research project was exempted from the approval of a Research Ethics Committee, in accordance with the National Health Council, Resolutions

Main results
Increasing trends were found for the detection rates of gestational and congenital syphilis in Paraná state and its health macro-regions, including in the analysis stratified by maternal age group; however, there was a decline during the COVID-19 period.

Implications for services
There is a need for strategic and immediate action by the state health services, focusing on expanding access and linkage to care, in order to ensure maternal and child well-being and reverse the rising trends observed.

Perspectives
Prevention and control actions towards the elimination of syphilis are needed to overcome these obstacles, directing efforts towards strengthening health education, early detection and appropriate treatment for pregnant women and their partners.

Setting
Paraná is the most populous state in the Southern region of Brazil, with a population of 11,444,380 inhabitants and a high human development index of 0.769 in 2021. 13In the context of implementing programs and actions and healthcare service provision, the state of Paraná is organized in a decentralized manner into four health macro-regions: Eastsubdivided into seven health regions -, West, Northwest and North -these with five regions each. 14

Participants and data source
Gestational and congenital syphilis records for the period f rom 2007 to 2021 were analyzed, taking into consideration data availability in the Notifiable Health Conditions Information System (Sistema de Informação de Agravos de Notif icação -SINAN) as of October 20, 2023, accessed through the Brazilian National health System Information Technology Department (Departamento de Informática do Sistema Único de Saúde -DATASUS); 15 data on the population of live births were also used, obtained f rom the Live Birth Information System (Sistema de Informações sobre Nascidos Vivos -SINASC), also via DATASUS. 15

Variables and statistical methods
The annual detection rates of gestational and congenital syphilis were calculated according to recommendations and criteria def ined by the Ministry of Health: 3 the total number of cases in pregnant women and children (numerator), according to the year of diagnosis, was divided by the total number of live births (denominator), in the same location and period; and the result was multiplied by 1,000.Rates were estimated by maternal age group [in years: ≤ 19 (young women); ≥ 20 (adult women)], given potential differences in trends between these groups; the denominator was related to maternal age recorded in SINASC.
Trend analysis was performed using segmented linear regression (joinpoint), with a maximum of two inflection points due to the number of years analyzed. 16Detection rates were considered as the dependent variable, and years of the series as the independent variable.The grid selection method was applied, transforming the dependent variable into the natural logarithm and adjusting the models to the standard errors of the rates and first-order autocorrelation, assessed according to the data. 16 the analysis of the series, we calculated the annual percent change (APC), which provided the increasing (positive) or decreasing (negative) trends at each joinpoint, the average annual percent change (AAPC), which consisted of the geometric mean of the APC, and 95% confidence intervals (95%CI), which indicated the significance of the APC or AAPC when they were different from zero. 16The analyses were performed using the Joinpoint Regression Program ® (version 5.0.2).

RESULTS
Between 2007 and 2021, a total of 13,861 cases of gestational syphilis and 6,643 cases of congenital syphilis were reported in the state of Paraná, representing detection rates, during the period, of 6.0/1,000 live births and 2.9/1,000 live births, respectively.The East (6.6/1,000live births) and West (6.9/1,000 live births) health macro-regions showed higher average detection rates of syphilis in pregnant women than the state as a whole (Figure 1A); for congenital syphilis, only the East health macroregion (3.4/1,000 live births) showed a higher average rate than Paraná (Figure 1B).

RESEARCH NOTE
Trend in gestational and congenital syphilis in Paraná state, 2007-2021  Moreover, all health macro-regions recorded an increase in the detection of gestational and congenital syphilis in the age group up to 19 years.Among adult women aged 20 years and older, similarly increasing trends were observed for gestational syphilis (AAPC = 21.3;95%CI 16.9; 31.9) and congenital (AAPC = 13.7;95%CI 11.9; 19.3) in Paraná; also in this age group, the health macroregions followed the statewide pattern (Table 2).

DISCUSSION
A pattern of increasing detection rates of gestational and congenital syphilis was observed in the state of Paraná in the period prior to 2019, regardless of the health macroregion and maternal age group.There was also a significant downward trend in almost all macro-regions evaluated during the years of the COVID-19 pandemic, possibly due to weaknesses related to detection and reporting in that emergency scenario. 17esent study has limitations inherent to secondary data, which are usually subject to underreporting, incompleteness, inconsistency and under-detection.This occurs mainly due to the possibility that any greater or lower detection or number of notifications, entrusted to health professionals, may lead to a significant or attenuated increase in rate trends.Strategies aimed at improving the quality and completeness of records may benefit future research and evidence-based decision-making.
Time series studies, using data f rom the SINAN, have highlighted increasing trends in maternal and child syphilis.In the state of Goiás, from 2007 to 2017, there was an increase in the occurrence among pregnant women (APC = 18.0; 95%CI 15.3; 20.8), as well as in congenital syphilis rates (APC = 16.8;95%CI 20.1; 33.8). 18Similarly, in Minas Gerais, an increasing trend was observed for detecting cases during pregnancy (APC = 36.7;95%CI 32.5; 41.0) and congenital syphilis cases (APC = 32.8;95%CI 28.0; 37.8), between 2009 and 2019. 19[22] Without disregarding the improvement of public policies for maternal and child care in Paraná, 23 aimed at the elimination of motherto-child transmission -and recognized with the achievement of the "bronze seal" -the f indings of this study raise an alert to the increasing incidence of congenital syphilis.[26] The predominance of gestational and congenital syphilis in the East and West health macro-regions of Paraná has already been reported. 9,27East macro-region encompasses

RESEARCH NOTE
Trend in gestational and congenital syphilis in Paraná state, 2007-2021   Curitiba, the capital of the state of Paraná, and its metropolitan region, which is more densely populated, while West macro-region is the border region between the state of Paraná, Brazil, Argentina and Paraguay.This factor should be taken into account when interpreting the calculated rates, since lower socioeconomic status has been associated with a higher likelihood of getting syphilis in the state. 27 can be concluded that the state of Paraná showed an increase in the detection rates of gestational and congenital syphilis, regardless of maternal age.This increase was more signif icant in the Northwest and North health macro-regions of the state.However, there was a decline during the COVID-19 pandemic.These f indings highlight the need for strengthening health education actions, 28 expanding testing and treatment for pregnant women and their partners, 29 and improving access to and close relationship to effective maternal and child care. 30pidemiologia e Serviços de Saúde, Brasília, 33:e2024188, 2024