The exact cause of gestational diabetes is not completely understood. It appears to have both a genetic basis[1] as well as environmental and lifestyle triggers (e.g., advanced age, diet, excessive weight gain, obesity, and physical inactivity).[2][3]
During pregnancy, the placenta secretes hormones (such as growth hormone, placental lactogen, progesterone, and corticotropin-releasing hormone) to ensure the fetus gets all the nutrients it needs. These hormones, alongside other metabolic changes, make the pregnant parent’s body less responsive to insulin, the hormone that allows glucose to leave the bloodstream and enter the body’s cells.[4] This is called insulin resistance. Normally, the pancreas secretes more insulin to combat this resistance and keep blood glucose under control. However, in some pregnant people, the pancreas is unable to secrete enough insulin to overcome the insulin resistance.[5][2] This causes blood sugar levels to rise beyond what is considered a healthy range and results in a diagnosis of gestational diabetes.