Gestational Diabetes Mellitus



  • Gestational diabetes mellitus (GDM) is the new onset of diabetes in the second half of pregnancy.
    • Maternity care providers should distinguish between GDM and previously unrecognized type 2 diabetes mellitus (T2DM).
    • GDM that persists beyond pregnancy should be reclassified as T2DM.
  • Class A1 refers to GDM controlled by diet and exercise (A1GDM).
  • Class A2 refers to pharmacologically managed GDM and implies suboptimal glycemic control (A2GDM).
  • GDM is associated with increased risks for preeclampsia, fetal macrosomia, shoulder dystocia, operative delivery, and subsequent T2DM and cardiovascular disease.



  • 6–8% of pregnancies in United States; may be as high as 25% with alternative diagnostic criteria (see “Diagnostic Tests & Interpretation”)
  • Highest among Hispanic, African American, Native American, Asian, and Pacific Islander women
  • Varies according to local prevalence of T2DM
  • Increasing globally

Etiology and Pathophysiology

  • The etiology of GDM is poorly understood.
  • During pregnancy, the placenta produces several hormones that can cause or exacerbate insulin resistance in susceptible individuals.


  • Incompletely understood
  • Strong family association
  • Polygenic risk plus environmental factors

Risk Factors

  • History of GDM in previous gestation
  • Previous delivery of baby weighing >4 kg
  • History of impaired glucose metabolism (A1c ≥5.7%, impaired glucose tolerance, or impaired fasting glucose)
  • Overweight or obese (BMI ≥25 kg/m2 or ≥23 kg/m2 in Asian Americans) who have any of the following risk factors:
    • Physical inactivity
    • Diabetes in first-degree relative
    • High-risk ethnicity (see “Prevalence”)
    • Cardiovascular disease
    • Hypertension
    • HDL cholesterol <35 mg/dL
    • Triglyceride level >250 mg/dL
    • Polycystic ovary syndrome
    • Other clinical conditions associated with insulin resistance (e.g., prepregnancy BMI >40 kg/m2, acanthosis nigricans)

General Prevention

  • Weight loss or maintain healthy weight before pregnancy
  • Regular exercise including both aerobic and resistance training (based on data from observational studies)

Commonly Associated Conditions

  • Prediabetes
    • Impaired fasting glucose
    • Impaired glucose tolerance
    • Hemoglobin A1c 5.7–6.4%
  • Hypertensive disorders of pregnancy
    • Gestational hypertension
    • Preeclampsia

There's more to see -- the rest of this topic is available only to subscribers.