What is Gestational Diabetes Mellitus (GDM)?
Gestational diabetes mellitus (GDM) is a type of diabetes that develops during pregnancy. It is different from having pre-existing diabetes before pregnancy.
When Does GDM Occur?
GDM generally occurs in the third trimester and is due to a combination of genetic and modifiable factors. During pregnancy, the body develops insulin resistance due to increased levels of hormones like progesterone, cortisol, and human placental lactogen (HPL), especially in the third trimester when fetal growth is rapid. Mild insulin resistance means the mother uses less glucose, allowing more to go to the baby. This is a normal physiological adaptation. However, if other risk factors for insulin resistance and/or decreased pancreatic function are present, GDM can develop.
Risk Factors for GDM
Similar to type 2 diabetes, GDM can be strongly influenced by genetic factors and modifiable factors such as dietary patterns high in saturated fat and highly processed foods, physical inactivity, and central adiposity. Increasing age, twin pregnancy, rapid weight gain in the first trimester, and certain ethnicities also increase the risk. GDM is on the rise in Australia and occurs in around 10% of pregnancies.
Blood Glucose Levels (BGLs) and Complications
BGLs can be high fasting, after meals, or both. High fasting BGLs are generally associated with a greater risk of complications, especially the baby being large for gestational age (LGA). If BGLs are not managed appropriately, especially if very high, there are higher rates of complications including stillbirth or uterine rupture. Other associated complications include gestational hypertension, pre-eclampsia, shoulder dystocia, neonatal hypoglycemia or respiratory distress, premature birth, and C-section delivery. Most of these risks, especially the more serious ones, are normalized if BGLs are managed adequately.
Managing GDM
The majority of GDM cases are mild, and 50-70% can be managed through dietary and exercise modifications alone. Some people, even if they adhere strictly to lifestyle recommendations, will need insulin. It’s important not to view this as a personal failure. Achieving good BGL control is the goal, and lifestyle management remains an important part of treatment even if insulin is required.
Postpartum Considerations
GDM generally resolves after birth, but there is an increased cardio-metabolic risk. Follow-up care and monitoring are essential, and I’ll discuss this in another post. 🙏