Overweight and obesity are increasing worldwide. This has major adverse consequences for health in general and fertility in women in particular. With the increasing number of women in reproductive age being obese, there is also an increasing need for fertility treatment. And with more pregnant women being obese, the amount of pregnancy complications will also continue to increase. In the USA, women with a body mass index (BMI) ≥ 35 kg/m² most frequently sought medical attention to become pregnant, but received surgical fertilityrelated services least frequent. Assisted reproductive technology (ART) is restricted worldwide beyond a certain BMI, ranging from 25 to 40 kg/m². In the Netherlands several fertility centres have a BMI limit, mostly around 30-35 kg/m². This restriction is based on different arguments from safety for the woman to risk for the future child. This thesis studies several aspects of reproductive problems in overweight and obese women. We address the (cost) effectiveness and safety of fertility treatment in overweight and obese women, the effectiveness of lifestyle intervention in obese women who suffer from subfertility, and we discuss ethical issues regarding fertility treatment in obese women.