Should I be screened for Gestational Diabetes Mellitus (GDM) at 23 weeks gestation given my family history of Type 2 Diabetes Mellitus (T2DM)?

GDM Screening at 23 Weeks with Family History of T2DM

Yes, you should be screened for gestational diabetes mellitus (GDM) now at 23 weeks gestation, given your family history of type 2 diabetes in a first-degree relative (your mother), which places you at higher than low risk for GDM. 1

Risk Assessment

You do not meet the criteria for "low risk" status that would exempt you from GDM screening. Low-risk women must meet ALL of the following criteria: 1

• Age <25 years
• Normal weight before pregnancy
• Member of ethnic group with low diabetes prevalence
• No known diabetes in first-degree relatives (you fail this criterion)
• No history of abnormal glucose tolerance
• No history of poor obstetrical outcomes

Your maternal history of type 2 diabetes is specifically identified as a risk factor requiring standard GDM screening at 24-28 weeks of gestation. 1, 2

Recommended Screening Approach at 23 Weeks

You should proceed with GDM screening now or within the next 1-5 weeks (optimal window: 24-28 weeks). 1 At 23 weeks, you are just at the lower edge of the standard screening window, making this an appropriate time to begin testing. 1

Two Screening Options Available:

Two-Step Approach (most common in US): 1, 2

• Initial 50-g glucose challenge test (non-fasting)
• If result ≥130-140 mg/dL, proceed to diagnostic 100-g oral glucose tolerance test (OGTT)
• GDM diagnosed if ≥2 values meet or exceed: fasting ≥95 mg/dL, 1-hour ≥180 mg/dL, 2-hour ≥155 mg/dL, 3-hour ≥140 mg/dL

One-Step Approach: 1, 2

• Single 75-g OGTT (fasting required)
• GDM diagnosed if ≥1 value meets or exceed: fasting ≥92 mg/dL, 1-hour ≥180 mg/dL, 2-hour ≥153 mg/dL

Important Distinction: You Do NOT Need Early Screening

While you have a family history risk factor, you do not meet criteria for "very high risk" that would have warranted screening earlier in pregnancy (first trimester or at initial prenatal visit). 1

Very high-risk criteria requiring early screening include: 1

• Severe obesity (BMI ≥30 kg/m²)
• Prior history of GDM or delivery of large-for-gestational-age infant
• Presence of glycosuria
• Diagnosis of polycystic ovary syndrome (PCOS)
• Strong family history of type 2 diabetes (your single first-degree relative qualifies you for standard screening, not early screening)

Why This Timing Matters for Outcomes

The 24-28 week window is physiologically optimal because insulin resistance peaks during this period of pregnancy, making GDM most detectable. 3, 4 The Hyperglycemia and Adverse Pregnancy Outcomes (HAPO) study demonstrated that maternal glycemia at 24-28 weeks shows continuous graded associations with adverse maternal, fetal, and neonatal outcomes—even within previously "normal" ranges. 1, 5

Untreated GDM increases risks of: 3, 5, 4

• Fetal macrosomia (large baby) leading to birth trauma
• Neonatal hypoglycemia
• Cesarean delivery
• Preeclampsia
• Future type 2 diabetes in both mother and child

Critical Follow-Up Regardless of Results

If screening is negative: You have completed appropriate GDM screening for this pregnancy. 1

If GDM is diagnosed: 1, 2, 5

• Initiate lifestyle modifications (nutrition counseling, moderate physical activity, glucose self-monitoring)
• Target glucose levels: fasting <95 mg/dL, 1-hour postprandial <140 mg/dL
• Add insulin therapy if targets not met with lifestyle alone
• Screen 4-12 weeks postpartum with 75-g OGTT using non-pregnancy diagnostic criteria
• Continue lifelong screening for diabetes at least every 3 years

Common Pitfall to Avoid

Do not delay screening beyond 28 weeks of gestation, as this reduces the window for effective intervention before delivery and increases risk of adverse outcomes. 1, 2 Your family history makes you ineligible to skip screening, even if you have no other risk factors. 1