A person develops gestational diabetes when their body cannot make enough insulin during pregnancy or when their body has become more resistant to the insulin it makes. Insulin is a hormone that transports glucose, or sugar, into the cells, which use it as energy. A person’s body will release hormones during pregnancy that result in changes such as weight gain. This results in the body reacting less effectively to insulin, which people call insulin resistance. This means that the body requires more insulin than usual.