Obesity is associated with metabolic complications such as insulin-resistance, type 2 diabetes, dyslipidemia, hypertension and polycystic ovary syndrome. Obesity adversely impacts fecundability and IVF outcomes through a variety of mechanisms, however even modest weight loss can improve situation. Pregnancy may be a significant health risk for morbidly obese women (BMI over 40 kg/m2) and fertility treatments are not recommended before weight loss. The fertile age of women is limited, therefore an efficient treatment of obesity should be chosen. For morbid obesity bariatric surgery combined with lifestyle changes is more efficient treatment than conservative treatment alone. Weight loss is associated with significant improvement in many parameters of reproductive function, chance to get pregnant improves and gestational risks decrease.