Gestational Diabetes

Gestational diabetes is a condition characterized by abnormal glucose tolerance and high blood sugar during pregnancy. It usually develops during the second or third trimester and resolves soon after delivery. Early identification of this condition is important, as it increases the risk of health complications for both the expecting parent and the baby when left untreated.^[1] This includes short-term risks (e.g., large for gestational age newborns, birth trauma, neonatal respiratory and metabolic complications, etc.)^[2][3] and long-term risks (e.g., type 2 diabetes and cardiovascular disease in the parent, and later-life obesity and type 2 diabetes in the offspring).^[4][5] Successful management of blood sugar greatly decreases the short- and long-term risks associated with gestational diabetes.^[6]

The symptoms of gestational diabetes, like fatigue, nausea, and increased thirst and urination, are often not noticed, as they are common during pregnancy.^[7] For this reason, screening for the signs of gestational diabetes is important.

High blood sugar is the main sign of gestational diabetes. It is detected by blood tests that measure the amount of glucose (sugar) in the bloodstream. There is also a blood test that can measure the amount of glucose attached to red blood cells. This is called glycated hemoglobin or hemoglobin A1c (HbA1c), and a high HbA1c is another sign of gestational diabetes. Since red blood cells survive in the bloodstream for about 2 to 3 months, testing the amount of sugar attached to them provides an indication of blood glucose concentrations over the past 2 to 3 months.^[7]

Pregnant people are screened for gestational diabetes at 24 to 28 weeks of gestation. Screening methods vary and may include a one- or two-step approach.^[8][9] The two-step approach is more common in the US. Both approaches use an oral glucose tolerance test (OGTT), which involves drinking a sugar-containing beverage and then taking blood samples to see how high blood sugar rises in response to the drink. If blood sugar levels are higher than established normal ranges, gestational diabetes may be diagnosed.

Some pregnant people have a higher risk of gestational diabetes and may be screened before 24 weeks gestation to identify pregestational diabetes (diabetes that was present before pregnancy) and early gestational diabetes. The best test for early screening is unclear, but fasting blood glucose levels, HbA1c values, and/or OGTT are often used.^[9][7]

Lifestyle change is the primary treatment for gestational diabetes.^[7] This involves medical nutrition therapy (an individualized diet plan), regular physical activity, and (if appropriate) weight management counseling. Blood glucose is monitored throughout the implementation of these interventions. If lifestyle changes alone do not adequately control blood glucose or there are signs of abnormal fetal growth, insulin may be prescribed to help lower blood glucose to achieve target ranges.^[7] Other drugs (e.g., metformin and sulfonylureas) are sometimes used, but more evidence is needed to fully understand their safety for the fetus (because these medications can cross through the placenta).^[10][7]

Yes, the effects of several supplements on gestational diabetes have been examined, including vitamin D,^[11][12] polyphenols,^[13] probiotics,^[11][14][15] myo-inositol,^[11][16] fish oil (including omega-3 fatty acids),^[11], etc. Of these, supplementation with vitamin D or myo-inositol during pregnancy may reduce the risk of gestational diabetes ^[11]. But there is currently no strong evidence to support the use of supplements to treat gestational diabetes.

Medical nutrition therapy (an individualized diet plan) is central to treating gestational diabetes and maintaining normal blood glucose levels.^[7][17] No evidence supports any single diet as optimal, so people with gestational diabetes should receive nutrition counseling from a registered dietitian to tailor their diet towards specific needs and goals. This is important because a variety of dietary modifications might improve maternal and/or infant health (e.g., the Dietary Approaches to Stop Hypertension diet).^[17]

Diet may also affect a pregnant person’s risk for gestational diabetes. Observational studies find that a dietary pattern rich in fruit, vegetables, whole grains, and fish, and low in red and processed meat, refined grains, and high-fat dairy reduced the risk of developing gestational diabetes.^{[18][19][11][11]}

Yes. Regular exercise during pregnancy can reduce blood glucose levels and the need for medications to treat gestational diabetes.^[20][21] Exercise may also reduce the risk of developing gestational diabetes.^[22][23] While exercise is safe during most uncomplicated pregnancies, a clinical evaluation is recommended before engaging in an exercise program.^[24]

The exact cause of gestational diabetes is not completely understood. It appears to have both a genetic basis^[25] as well as environmental and lifestyle triggers (e.g., advanced age, diet, excessive weight gain, obesity, and physical inactivity).^[26][27]

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.^[28] 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.^[29][26] This causes blood sugar levels to rise beyond what is considered a healthy range and results in a diagnosis of gestational diabetes.