Gestational diabetes mellitus is the type of diabetes that occur during pregnancy and ended after pregnancy in many cases. The term gestation was used in the late twenty centuries. The release of glucose increases during the normal pregnancy and insulin releases from the pancreas and control the glucose level. During gestational period, the insulin release fell down and glucose molecules are not properly breakdown into their substrates. The prevalence of GDM has been observed in the age group of 27 years. GDM affect both children and mother as it causes retinopathy, neuropathy and CVDs. In children, it causes the broad shoulder of fetus and can affect many organs of baby. The high level of glucose can cause complications during delivery. Insulin therapy and metformin are safe treatment for the gestational diabetes. The mechanism underlying the effect cause in the fetus due to gestational diabetes are still known. The studies can be done to find out these mechanisms.