Diabetes that develops for the first time in pregnancy is called gestational diabetes and affects between two and seven percent of pregnant women. In this condition, the pancreas produces insufficient insulin to move glucose (sugar) from the blood to be stored, resulting in high levels of glucose in the blood. It usually begins at 20-24 weeks of pregnancy. The risk is greater if you have a family history of late-onset diabetes, or you have previously had a large baby, a stillbirth, or gestational diabetes.
Insulin levels become inadequate due to the extra demands of the fetus and because hormones produced by the placenta block the effects of insulin.
What might be done
Between 24 and 28 weeks, you will be tested for gestational diabetes. If you have risk factors, you may take this test earlier. The test involves having a blood test in the morning after fasting, then drinking a special sugary drink and having a repeat blood sugar check one hour later. If you have high levels of glucose, you'll have to take a similar, but longer test to confirm a diagnosis. If you do have gestational diabetes, you will be taught how to test blood glucose at home. In most cases, the diabetes can be controlled through diet and exercise. However, if these measures prove inadequate you may need insulin injections until the end of pregnancy. Extra scans may be done to check the baby's growth, and early induction (see Induction of Labor) may be advised.
If you've had gestational diabetes previously, it's important to ensure that your weight is normal before you become pregnant again.