Testing for gestational diabetes (GDM) is a routine part of prenatal care. If you’ve ever been pregnant, you’ll likely recall drinking a sticky, sweet, orange or cola drink midway through the second trimester and getting your blood drawn after a set amount of time. If the blood test was normal, you may never have given GDM much thought. GDM is a signal that you are at risk to develop diabetes again later in life, and can serve as a wakeup call to make healthy lifestyle changes to potentially prevent it.
Blood Sugar Control 101
Our bodies need insulin, produced by the pancreas, to process sugar and carbohydrates from our diet. When the body either cannot make or cannot respond appropriately to insulin, diabetes develops and blood sugar becomes elevated. Most people who cannot produce insulin develop type 1 diabetes at a young age and require insulin shots throughout their lives. Insulin resistance — type 2 and gestational diabetes — can develop at any time. Pregnancy is a time when our bodies are more resistant to the effects of insulin.
The placenta is a hormone-producing factory. In addition to hormones that induce nausea and emotional lability during pregnancy, the placenta produces human placental lactogen (HPL), which induces insulin resistance. As pregnancy progresses, HPL levels rise, resulting in more resistance to the effects of insulin. Screening for GDM typically occurs in the second trimester of pregnancy (24 to 28 weeks) since earlier testing would miss the diagnosis in many women. If the result is elevated compared to a reference value, a three-hour test with hourly blood tests follows to determine if you have gestational diabetes. Some doctors are using a newer, one-step, two-hour fasting test. Your doctor may recommend earlier testing if you have had prior pregnancies with diabetes or a large baby, if you are of a particular ethnicity, if there’s a family history of diabetes or if you are significantly overweight. In addition, even if the initial screening is negative, repeat testing may be recommended if concern for diabetes is raised later on in pregnancy.
We are so vigilant about identifying GDM because of the serious implications for both mother and baby. Unidentified and untreated GDM will result in persistently elevated blood sugars in mom and an increased risk of a large baby, birth injury, C-section and even stillbirth. Newborns are also at higher risk of breathing problems, low blood sugar and jaundice. Early diagnosis and treatment can prevent most of these problems.
Treating Pregnancy Diabetes
Once the GDM diagnosis is made, the treatment is multifaceted. Women will be taught to check their blood sugars with a home monitor throughout the day using a small blood sample from a finger pinprick. Diet modification and exercise play a central role in treatment and can sometimes preclude the need for medication. If blood sugars are persistently elevated, insulin injections are the mainstay of treatment. Some doctors prescribe oral medications that work by increasing insulin sensitivity, but these have less data in pregnancy and may not be as effective. In the presence of GDM, periodic ultrasound testing for fetal well-being and growth is typically done in the third trimester.
Although GDM usually resolves after delivery, close follow-up is crucial. Medications and blood sugar monitoring are typically stopped postpartum, but a diabetes-screening test should be performed at six weeks and periodically recommended thereafter for the presence of non-gestational, or type 2, diabetes. Up to half of all women with GDM will develop type 2 diabetes in the decades after delivery. The best way to reduce your risk of GDM and type 2 is with a healthy lifestyle, including maintaining a healthy weight and diet, and getting plenty of exercise.
Hayley Solomon Quant, MD, is a clinical fellow in Obstetrics, Gynecology and Reproductive Biology at Harvard Medical School, and a resident in Obstetrics and Gynecology at Beth Israel Deaconess Medical Center, Boston, MA.