Gestational diabetes mellitus
Risk factors include prior pregnancy with GDM, maternal obesity, race other than White, excessive weight gain in pregnancy, older than average maternal age, polycystic ovarian syndrome (PCOS), hypertension, preeclampsia, and preexisting glucose intolerance.
Testing in the United States is typically conducted between 24 and 28 weeks' gestation via a 50-g glucose load and a blood sugar check at the 1-hour mark. This typical definition means that the patient will not be diagnosed until after approximately 20 weeks' gestation. The reasoning is that if early blood glucose values are elevated, it may be related to underlying, previously unrecognized glucose intolerance or type 2 diabetes. Early screening (at < 20 weeks' gestation) for diabetes should be considered for any patients with a body mass index (BMI) over 30 and any of the following risk factors:
- Prior pregnancy with GDM
- Prior infant weighing 4000 g or more
- Ethnicity with higher risk of GDM (African American, Latino, Native American, Asian American, Pacific Islander)
- History of cardiovascular disease and elevated hemoglobin A1c (greater than or equal to 5.7%)
Classifications for GDM include:
- Diet controlled or A1 – blood sugars can be controlled with diet alone
- A2 – medication is needed to control blood sugars
O24.919 – Unspecified diabetes mellitus in pregnancy, unspecified trimester
11687002 – Gestational diabetes mellitus
- Beware that an early glucose test (done at less than 20 weeks' gestation) could actually represent underlying glucose intolerance or previously undiagnosed type 2 diabetes.
- Beware the possibility of screening for routine GDM too early in pregnancy (false negative).
- Beware the possibility of an abnormal value due to the initial glucose screen not being a fasting test (false positive).