Risk Factors for Gestational Diabetes
Women at high risk for gestational diabetes include those with marked obesity, personal history of GDM, glycosuria, or strong family history of diabetes, and these patients should undergo glucose testing as soon as feasible at their first prenatal visit. 1
High-Risk Clinical Characteristics Requiring Early Testing
The following factors identify women who need immediate glucose screening at their first prenatal visit 1:
- Marked obesity (BMI >25 kg/m²) 1
- Personal history of gestational diabetes 1
- Glycosuria 1
- Strong family history of diabetes (first-degree relative) 1
Major Risk Factors
Age
- Age >25 years is an established risk factor 1
- Increased maternal age independently increases GDM risk 1, 2
Obesity and Weight
- Prepregnancy BMI >25 kg/m² carries an odds ratio of 4.14 for developing GDM 2
- Maternal prepregnancy BMI is an independent risk factor for adverse outcomes 1
- Development of type 2 diabetes after GDM increases 18% per unit of BMI increase from prepregnancy BMI 3
Ethnicity
- Hispanic, Native American, South or East Asian, African American, or Pacific Island descent are at increased risk 1, 4, 5
- Certain ethnic groups (e.g., some Native-American groups) have sufficiently high prevalence to warrant one-step diagnostic testing 1
Obstetric History
- Previous history of GDM significantly increases risk 1, 4
- Having GDM in two pregnancies increases risk with hazard ratios ranging from 4.35 to 15.8-fold compared to single GDM pregnancy 3
- History of macrosomia (previous large-for-gestational-age infant) carries an odds ratio of 2.72 2
- Previous adverse pregnancy outcomes related to GDM 1
- Higher parity (third or subsequent pregnancy) carries an odds ratio of 1.8 2
Family History
- Family history of diabetes in first-degree relatives carries an odds ratio of 1.76 2
- This is consistently identified as a major risk factor across guidelines 1, 4
Low-Risk Characteristics (No Testing Required)
Women meeting ALL of the following criteria are considered low-risk and may not require glucose testing 1:
- Age <25 years 1
- Normal weight before pregnancy (BMI ≤25 kg/m²) 1
- White ethnic origin 1
- No family history of diabetes in first-degree relatives 1
- No history of glucose intolerance 1
- No history of adverse pregnancy outcomes related to GDM 1
Important Clinical Considerations
Prevalence by Risk Status
- Low-risk women: GDM prevalence ranges from 1.4% to 2.8% 1
- High-risk women: GDM prevalence ranges from 3.3% to 6.1% 1
- Overall prevalence ranges from 1% to 14% depending on population characteristics 1
Critical Pitfall
Selective screening based on risk factors alone would miss 43% of gestational diabetes cases, including 28% who would require insulin therapy. 6 This finding demonstrates that gestational diabetics with and without traditional risk factors have similar rates of requiring insulin, macrosomia, and cesarean delivery 6. Therefore, universal screening is recommended rather than risk-based selective screening 6.
Metabolic and Pathophysiologic Factors
- Obesity and factors promoting insulin resistance enhance risk 1, 7
- Markers of islet cell-directed autoimmunity are associated with increased risk of type 1 diabetes after GDM 1, 7
- Women with GDM share characteristics with metabolic syndrome, including glucose intolerance, insulin resistance, central obesity, elevated triglycerides, and low HDL cholesterol 7
Long-Term Risk Context
Women with GDM have a 10-fold increased risk of developing type 2 diabetes compared to women without GDM, with a lifetime risk of 50-60% 3, 7. This underscores the importance of identifying all women with GDM, not just those with obvious risk factors 3, 7.