Contraceptive Failure in Brazil: Magnitude, Associated Factors, and Consequences

• Grant number: 25/05470-2
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: October 01, 2025
• End date: September 30, 2027
• Field of knowledge: Health Sciences - Collective Health - Public Health
• Principal Investigator: Ana Luiza Vilela Borges
• Grantee: Fernanda Gontijo Araújo
• Host Institution: Escola de Enfermagem (EE). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Research problem: Contraceptive failure is one of the components of contraceptive discontinuation. It refers to the occurrence of pregnancy while using contraceptives and is one of the main contributors to unintended pregnancy worldwide. In Brazil, the latest nationwide data on contraceptive failure date back to 1996. Currently, despite the high prevalence of contraceptive use, more than 50% of pregnancies are unintended, which may be partly due to contraceptive failure. Objective: To assess the magnitude, associated factors, and consequences of contraceptive failure in Brazil. Methods: Two epidemiological studies with different methodologies are proposed. The first will use data collected through the contraceptive calendar from 2015 to 2017 among women aged 18 to 49 years from primary health care facilities in three capital cities (n=2051). The contraceptive failure rate will be estimated over a 12-month period from the start of method use using Kaplan-Meier survival curves, and associated factors will be analyzed using a Cox regression model. The second study, a population-based survey, will use data from the 2023 Brazilian Demographic and Health Survey. The subsample will consist of women aged 15 to 49 who had a live birth in the 60 months prior to the interview. The occurrence of failure will be estimated based on the question: "when you became pregnant, were you using any method to prevent pregnancy?". Logistic regression models will be used to analyze the factors associated with contraceptive failure. In all analyses, the effect of the complex sampling design will be considered. Expected results: The findings may help fill gaps in the understanding of contraceptive dynamics, revealing the contribution of contraceptive failure to unintended pregnancies, its consequences, which methods have higher failure rates, and which population groups are most affected.