Class III female obesity impairs both natural and assisted conception and increases obstetric complications and postnatal chronic diseases in the offspring, leading to higher economic costs. Weight reduction before conception may improve these undesirable outcomes. To date, no well-designed randomised trials of intervention programs for weight reduction with adequate follow-up and monitoring by a multidisciplinary team and a significant number of patients have been published in the field of assisted reproduction. Considering the demonstrated economic and health consequences, morbidly obese women should be refused fertility treatment. However, weight loss options, associated infertility factors and ethical considerations should also be taken into account in the decision-making process.