During pregnancy, the placenta produces hormones to sustain your pregnancy. A side effect of these hormones is that your cells become more resistant to insulin. As your placenta grows larger in the second and third trimesters, it secretes more of these hormones — making it even harder for insulin to do its job.

Normally, your pancreas responds by producing enough extra insulin to overcome this resistance. When you have gestational diabetes, your pancreas can't keep up. Without enough insulin the glucose from the food you eat isn't transferred into your cells. The glucose builds up in your blood causing problems.

Although this form of diabetes usually disappears after the birth of the baby, women who have had gestational diabetes have a 40 to 60% chance of developing type 2 diabetes within 5 to 10 years. Maintaining a reasonable body weight and being physically active may help prevent development of type 2 diabetes.
About 3 to 8 percent of pregnant women develop gestational diabetes. Women with gestational diabetes may not experience any symptoms. Your doctor is likely to do routine diabetes testing during your pregnancy.
Risk factors
Any pregnant woman can develop gestational diabetes, but some women are at greater risk than are others. Risk factors for gestational diabetes include:
  • Age. If you are older than age 25, you are at increased risk
  • Family history. Your risk increases if you have a close family member, such as a parent or sibling, has type 2 diabetes
  • Personal History. You're also at greater risk if you had gestational diabetes during a previous pregnancy or you had pre-diabetes before becoming pregnant
  • Prior Birth Giving. Your risk increases if during a previous pregnancy, you delivered a very large baby or you had an unexplained stillbirth
  • Weight. Being overweight before pregnancy increases your risk
  • Race. For reasons that aren't clear, women who are black, Hispanic, American Indian or Asian are more likely to develop gestational diabetes
Complications of gestational diabetes
Most women who have gestational diabetes deliver healthy babies. However, untreated or uncontrolled blood sugar levels can cause problems for you and your baby.
Complications for your baby can occur as a result of gestational diabetes:
  • Excess growth. Extra glucose can cross the placenta, which triggers your baby's pancreas to make extra insulin. This can cause your baby to grow too large (macrosomia). Very large babies are more likely to become wedged in the birth canal, sustain birth injuries or require a C-section birth.
  • Low blood sugar. Sometimes babies of mothers with gestational diabetes develop low blood sugar (hypoglycemia) shortly after birth because their own insulin production is high. Prompt feedings and sometimes an intravenous glucose solution can return the baby's blood sugar level to normal.
  • Respiratory distress syndrome. If your baby is delivered early, respiratory distress syndrome — a condition that makes breathing difficult — is possible. Babies who have respiratory distress syndrome may need help breathing until their lungs become stronger.
  • Jaundice. This yellowish discoloration of the skin and the whites of the eyes may occur if a baby's liver isn't mature enough to break down a substance called bilirubin, which normally forms when the body recycles old or damaged red blood cells. Although jaundice usually isn't a cause for concern, careful monitoring is important.
  • Type 2 diabetes later in life. Babies of mothers who have gestational diabetes have a higher risk of developing obesity and type 2 diabetes later in life.
  • Death. Rarely, untreated gestational diabetes results in a baby's death either before or shortly after birth.
Complications for you can also occur as a result of gestational diabetes:
  • Preeclampsia. This condition is characterized by high blood pressure and excess protein in the urine. Left untreated, preeclampsia can lead to serious or even life-threatening complications for both mother and baby.
  • Subsequent gestational diabetes. Once you've had gestational diabetes in one pregnancy, you're more likely to have it again with the next pregnancy. You're also more likely to develop diabetes — typically type 2 diabetes — as you get older.
  • Guide to Gestational Diabetes