The absolute power of relative risk in debates on repeat cesareans and home birth in the United States

Abstract

Background: Changes in policies and practices related to repeat cesareans and home birth in the U.S. have been influenced by different interpretations of the risk of poor outcomes.

Methods: This article examines two cases-vaginal birth after cesarean (VBAC) and home birth to illustrate how an emphasis on relative over absolute risk has been used to characterize outcomes associated with these practices. The case studies will rely on reviews of the research literature and examination of data on birth trends and outcomes.

Results: Childbirth involves some unique challenges in assessing health risks, specifically the issues of: (1) timing of risks (lowering health risk in a current birth can increase it in subsequent births); (2) the potential weighing of risks to the mother's versus the infant's health; (3) the fact that birth is a condition of health and many of the feared outcomes (for example, symptomatic uterine rupture) involve very low absolute risk of occurrence; and (4) a malpractice environment that seizes upon those rare poor outcomes in highly publicized lawsuits that receive widespread attention in the clinical community. In the cases of VBAC and home birth, the result has been considerable emphasis on relative risks, typically an adjusted odds ratio, with little consideration of absolute risks.

Conclusion: Assessments of the safety of interventions in childbirth should involve careful consideration and communication of the multiple dimensions of risk, particularly a balancing of relative and absolute risks of poor health outcomes.