During pregnancy, some women develop high levels of blood sugar, a condition known as gestational diabetes, or gestational diabetes mellitus. Gestational diabetes typically occurs between the 24th and 28th weeks of pregnancy. According to the American Diabetes Association, gestational diabetes typically affects 18 percent of all pregnant women (ADA).
Having gestational diabetes does not necessarily mean that you had diabetes before your pregnancy or that you will have it after you give birth.
The exact cause of gestational diabetes is unknown, but experts believe hormones play a role.
During pregnancy, a woman’s body produces larger amounts of some hormones: human placental lactogen, estrogen, and cortisol. These hormones develop in the placenta and help to sustain the pregnancy.
Over time, the amounts of these hormones increase. They may interfere with the action of insulin, the hormone that regulates blood sugar. Insulin helps move glucose out of the blood and into the body cells, where it is used for energy. Without enough insulin, or with a high level of hormones that prevent insulin from working effectively, blood glucose levels go up, causing gestational diabetes.
The following can all increase your risk for gestational diabetes:
- being overweight prior to pregnancy
- a family history of diabetic disorders
- having previously given birth to large babies (more than nine pounds)
- being over the age of 25
- having too much amnitiotic fluid
- having had an unexplained miscarriage or stillbirth
- having high blood pressure
As rates of type 2 diabetes in younger women have been rising, the American Diabetes Association recommends that women at risk for diabetes be tested for diabetes at the beginning of a pregnancy. These risks factors include:
- being overweight
- being sedentary
- having a family history of diabetes
- having low good (HDL) cholesterol or high triglycerides levels
- being a member of a higher-risk ethnic group (people of African, Latino, Asian, Native American, or Pacific Islander descent)
- having high blood pressure
- previous gestational diabetes or having given birth to a baby who weighed more than 9 pounds
- past history of prediabetes or signs of insulin resistance
Women who have no risk factors and who have normal sugar levels at the beginning of a pregnancy will be retested between the 24th and 28th weeks of pregnancy.
It is rare for gestational diabetes to cause symptoms. Symptoms that do occur are usually mild.
Symptoms of high blood sugar levels include:
- excessive thirst
- blurred vision
- excessive need to urinate
- weight loss even when eating properly
- infections in the bladder and other body areas
- vomiting and nausea that is not associated with normal pregnancy
To diagnose gestational diabetes, your doctor will do either a one-step oral glucose tolerance test or a two-step oral glucose tolerance test.
For the one-step test, you will have your fasting sugar levels tested and then drink a solution containing 75 grams of carbohydrates. You will then have your blood sugar levels tested at both the one-hour mark and the two-hour mark. Gestational diabetes is diagnosed if you have any one of the following sugar values:
- fasting sugar level greater than or equal to 92 mg/dL
- one-hour sugar level greater than or equal to 180 mg/dL
- two-hour sugar level greater than or equal to 153 mg/dL
For the two-step test, you will have your fasting sugar tested and then drink a solution containing 50 grams of sugar. You will have another test after an hour, and if your glucose is greater than or equal to 140 mg/dL, you will do a second test on a different day. For this test, you will have your fasting sugar tested, and then you will drink a solution with 100 grams of sugar in it. You will then have your sugar tested again at the one-, two-, and three-hour marks. Gestational diabetes is diagnosed if you have at least two of the following values:
- fasting sugar level greater than or equal to 95 mg/dL or 105 mg/dL*
- one-hour sugar level greater than or equal to 180 mg/dL or 190 mg/dL*
- two-hour sugar level greater than or equal to 155 mg/dL or 165 mg/dL*
- three-hour sugar level greater than or equal to 140 mg/dL or 145 mg/dL*
(Different organizations may recommend different guidelines.)
Your treatment often depends on the oral glucose tolerance test results. In most cases, you may need to follow your doctor’s management plan, which includes eating healthy and exercising.
Some women are prescribed insulin injections until delivery. If you do start taking insulin, be sure to talk to your doctor or healthcare provider about properly timing your meals and exercise to avoid low blood sugar. Also talk to your healthcare provider so you know exactly what to do if your blood sugar levels fall too low, or if they are consistently higher than they should be.
You may be advised to monitor your glucose levels daily. Your physician may supply you with a special glucose-monitoring device.
Depending on your overall health and ability to move about, your doctor may suggest that you do light to moderate exercise in order to manage your blood sugar levels after meals.
If blood sugar levels are higher than target throughout the pregnancy, complications can occur at delivery. Your baby may experience some complications if you do not follow your doctor’s treatment plan. These complications include:
- large size at birth
- breathing difficulties
- low blood sugar
Your baby may also be at higher risk of developing diabetes later in life.
Your blood sugar will return to normal after you give birth. Mothers who had gestational diabetes are at greater risk for type 2 diabetes and obesity.