Gestation is the length of a pregnancy from conception to birth (usually 40 weeks in humans). Gestational diabetes is a type of diabetes (glucose intolerance) that occurs in some women during pregnancy. Women with gestational diabetes have a high level of glucose (or sugar) in their blood because they do not have enough of the hormone insulin to cope with the extra demands of the growing foetus (unborn baby). In most cases, gestational diabetes is managed by diet and exercise and will usually disappear after the baby is born.