Gestational Diabetes Mellitus
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- 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
- 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
- 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)
- 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
- Impaired fasting glucose
- Impaired glucose tolerance
- Hemoglobin A1c 5.7–6.4%
- Hypertensive disorders of pregnancy
- Gestational hypertension