This chapter focuses on implications of bariatric surgery and gestational diabetes. The prevalence of obesity is increasing all over the world. Obesity has significant negative impact on health by increasing rates of diabetes, hypertension, cardiovascular diseases, and degenerative joint disease. Incidence of bariatric surgery (BS) is increasing day by day because of increasing prevalence of obesity, easy laparoscopic access, and financial availability. This chapter covers the pathophysiology of effect of obesity on development of gestational diabetes mellitus, overview of bariatric surgeries, fetomaternal complications of maternal obesity, and effect on development of gestational diabetes mellitus. Bariatric surgery, now known as metabolic surgery is a promising option to cure obesity and associated co-morbidities like DM. Pregnancy after BS has less risk of developing gestational diabetes mellitus (GDM) but requires constant monitoring and supervision through a multidisciplinary team approach.