Investigation of adverse outcomes in obstetrics and gynaecology requires a systematic and systemically oriented approach. The main objective of these assessments is to decrease their incidence. Lethal complications in obstetrics and gynaecological surgery have become so rare in developed countries that we have to grapple mainly with severe morbidities. A model for such investigation is presented, based on answers to 3 questions: What? How? and Why? These questions correspond to 3 components of quality assurance: Outcome, Process, and Structure, respectively. Aspects of Reason's model of accidents are also included, in the form of "active failures" and "latent conditions." The latter are divided into basic contributory factors, 4 of which are derived from a model of human factors influencing behaviour in anaesthesia or flight-crew environments. To illustrate its basic nature, the model is applied to anonymized cases of surgical complications. Application of the model to the reactive investigation of close calls is discussed, as is application to the proactive interrogation of the care system for the presence and nature of hazards that pose threats to safety.