Lifestyle is increasingly recognized as an outcome-determining factor in assisted reproduction, not only with regard to the cost-effectiveness but also in view of the balance of benefits and risks, including risks related to the welfare of the future child. This document briefly summarizes the evidence concerning the impact of three lifestyle-related factors (obesity, tobacco smoking and alcohol consumption) on both natural and assisted reproduction (IVF) and discusses the implications of this for the practice of medically assisted reproduction in the light of relevant ethical principles. The central question is whether and to what extent fertility treatment of obese, smoking or drinking patients should be made conditional on prior lifestyle changes.