Abortion and health in Brazil: challenges to research within a context of illegality.

Abortion research faces great challenges, even more so in contexts in which it is illegal. Women tend to omit the voluntary termination of pregnancy or to declare having miscarried, which results in an underestimation of abortions. Research on this subject is indispensable because it enables us to estimate the incidence of abortion and its complications, and to identify unmet demands and more vulnerable groups so as to subsidize health actions and policies. In this article, we seek to describe the main challenges faced by researchers through a review of original studies on abortion and our reflections based on empirical studies we have conducted. We discuss the difficulties in obtaining information, strategies and techniques used to increase accuracy and reliability and their limits and advantages, and strategies for estimating the occurrence of abortion and its complications, using direct (interviews and data from medical charts) and indirect (secondary data on mortality and morbidity) methods. When investigating abortion complications, we address studies on mortality and morbidity, emphasizing the specificities of abortion among obstetric causes. We discuss the main indicators used by researchers and methodological aspects of their construction. We make recommendations for overcoming methodological problems and conducting new studies. In the conclusion, we reiterate the relevance of research on abortion and the need for approaches that contemplate its complexity.