Excessive obesity not only affects the physical appearance, but also causes type 2 diabetes, coronary heart disease, hypertension and other diseases, and is inextricably linked to fertility. The most important reason for infertility due to excessive obesity is that it affects ovulation. Obesity can lead to increased levels of leptin and insulin resistance in women, and if obesity persists over time, it can eventually lead to ovulation. Many women have irregular menstruation when they are fat and return to normal menstruation after losing weight for this reason. Polycystic ovary syndrome is also a common cause of infertility, and patients with polycystic ovary syndrome tend to be obese. Obesity can aggravate the non-ovulatory condition of polycystic ovaries, therefore, patients with polycystic ovary syndrome who are overweight are advised to lose weight before preparing for pregnancy. If the patient is already obese with a large base and the usual weight loss methods cannot control the weight, this is the best time to lose the extra weight through weight loss metabolic surgery. Data show that weight loss metabolic surgery is the most effective treatment as morbid obesity, and weight loss surgery significantly improves polycystic ovary syndrome, irregular menstruation, hirsutism, and infertility. It can quickly relieve insulin resistance and hyperinsulinemia, and has good effect on obesity complications including polycystic ovary syndrome. Bariatric surgery improves fertility, menstrual irregularities are improved by 50%, and 30% of hirsutism is improved. The incidence of polycystic ovary syndrome is reduced by 40%. There is also a decrease in androgens, an increase in sex hormone binding globulin, an increase in luteinizing hormone and follicle stimulating hormone levels, and an improvement in ovulatory function. Studies have shown that patients with polycystic ovary syndrome have higher pregnancy rates and lower miscarriage rates after weight loss surgery. Therefore, it is best for women who are overweight to lose weight before getting pregnant.