ABSTRACT Objective: To analyze the trend in the detection rate of Syphilis in Pregnant Women (SP) and in the incidence rate of Congenital Syphilis (CS) in the state of Ceará. Methods: This is an ecological study that used the technique of interrupted time series to analyze monthly data on cases of SP and CS obtained from the Department of Informatics of the Brazilian Unified Health System (DATASUS) from January 2015 to July 2021. The Kernel test and the Lincoln-Petersen estimate were used to analyze the statistical significance. Results: In 2015, a monthly detection rate of SP was estimated at 5.4 and a CS incidence rate of 8.2 per one thousand live births (LB). The implementation of the ordinance that changed the criteria for defining cases of SP and CS resulted in an increase of 4.9 (p<0.0001; 95%CI; 3.33; 6.61) in the detection rate of SP and a decrease of 0.1 on the incidence of CS (p<0.001; 95%CI -0.2; -0.1). The COVID-19 pandemic did not impact the monthly detection rate of SP (p=0.558; 95%CI 5.92; 3.22), nor its trend (p=0.7397; 95%CI 0.28; 0.3), but there was an increase of 0.19 in CS (p<0.001; 95%CI 0.1; -0.31). Conclusion: Between 2015 and June 2021, the trend in the detection rate of SP and in the incidence rate of CS was impacted by changes in the criteria for defining cases of these diseases proposed by the Brazilian Ministry of Health and the COVID-19 pandemic.