II. Epidemiology: Prevalence
- Overall: 6 to 9% of pregnant women in U.S. (2017)
- Incidence doubled between 2006 and 2017
- High risk groups (see below): 14%
III. Pathophysiology
- Pancreatic Beta cell hyperplasia is normal in pregnancy
- Placental Hormones increase Insulin Resistance (esp. third trimester)
- Gestational Diabetes results when increased beta cell function does not overcome Insulin Resistance
IV. Risk Factors
- Maternal Age > 35 years old (OR 1.6)
- Family History of Diabetes Mellitus in first degree relative (RR 1.7)
- Body Mass Index >25 kg/m2 (OR 3.2) and esp. BMI >40 kg/m2
- Weight gain >11 lb (5 kg) since 18 years old (RR 1.7)
- Personal History of Diabetes Mellitus
- See Diabetes Mellitus Preconception Counseling
- Previous abnormal lab testing
- Gestational Diabetes diagnosis in prior pregnancy (OR 13.2)
- Glucose Challenge Test (GCT)
- Glucose Tolerance Test (GTT)
- Glycosuria (Urine Glucose positive)
- Symptoms of Diabetes Mellitus
- Polyuria (pre-pregnant)
- Polydypsia
- Blurred Vision
- Prior Pregnancy Complication
- History of infant with Macrosomia (OR 1.4)
- Weight exceeds 4000 grams or 9 pounds
- Excessive gestational weight gain (OR 1.4)
- History of infant with Congenital Anomaly
- Prior Stillbirth
- Habitual Abortions
- Preeclampsia
- Polyhydramnios
- History of infant with Macrosomia (OR 1.4)
- Ethnicity
- Asian (RR 2.3)
- Native American (RR 2.1)
- Pacific Islander (RR 2.1)
- Black (RR 1.8)
- Hispanic (RR 1.5)
- Other associated factors
- References
V. Labs: Screening - Two Step
- Alternative to Two step screening is a single Glucose Tolerance Test 2 hour (OGTT)
-
Glucose Challenge Test (GCT)
- Non-Fasting patient drinks 50 grams of Glucose and has Serum Glucose drawn at 1 hour
- Abnormal if Serum Glucose exceeds 130 mg/dl (some organizations use 140 mg/dl cutoff)
- Empiric Gestational Diabetes Management for GCT >200 mg/dl (without a 3 hour GTT)
- Timing of Test
- High Risk (See Risk Factors above)
- Test at initial Antepartum Visit to identify preexisting, undiagnosed Diabetes Mellitus (choose one)
- Hemoglobin A1C >=6.5% Preexisting Diabetes (>5.9% Glucose Intolerance) OR
- Fasting plasma Glucose >=126 mg/dl preexisting diabetes (>110 mg/dl Glucose Intolerance) OR
- Abnormal Glucose Tolerance Test 2 hour (OGTT)
- Rescreen GCT at 24-28 weeks for Gestational Diabetes if initially negative
- Test at initial Antepartum Visit to identify preexisting, undiagnosed Diabetes Mellitus (choose one)
- Low Risk
- Perform GCT at 24-28 weeks
- Other Indications
- May be considered later in pregnancy for polyhydramnios
- High Risk (See Risk Factors above)
-
Glucose Tolerance Test 3 hour
- Indicated for abnormal Glucose Challenge Test
- Fasting patient drinks 100 grams of Glucose
- Serum Glucose drawn Fasting, 1,2, 3 hours
- Interpretation
- See Glucose Tolerance Test
- Abnormal if 2 or more readings over respective cut-offs
- Thresholds for Fasting and 1, 2, and 3 hours
VI. Management
VII. Complications: Fetal
-
Fetal Macrosomia with weight > 4000 grams (RR 1.6)
- Large for Gestational Age (LGA) >90th percentile
- Operative delivery risk (Ceserean section)
- Shoulder Dystocia or other Birth Trauma risk (RR 2.9)
- Hypoglycemia
- Hypothermia
- Hyperbilirubinemia
- Hypocalcemia
- Premature birth
- Respiratory distress syndrome
- Polycythemia Vera (plethora)
- Obesity during childhood (RR 1.5)
- Birth defects (RR 1.2)
VIII. Complications: Maternal
- Longterm risk of developing Diabetes Mellitus
- Consider periodic Diabetes Screening, Prediabetes and lifestyle management
- Bellamy (2009) Lancet 373(9677):1773-9 +PMID:19465232 [PubMed]
- Gestational Diabetes Mellitus in future pregnancy (RR 7.4)
- Gestational Hypertension (RR 1.6)
- Preeclampsia (RR 1.5)
- Ceserean Section (RR 1.3)
IX. Prognosis
- See Gestational Diabates perinatal mortality
- Adverse perinatal outcomes (see above) include infant death, Shoulder Dystocia, Fracture, nerve palsy
- Maternal and fetal outcomes are significantly improved with good Blood Sugar control
- Adverse perinatal outcomes are reduced from 4% without treatment to <1% with treatment
- Crowther (2005) N Engl J Med 352(24): 2477-86 [PubMed]
- Metzger (2008) N Engl J Med 358(19): 1991-2002 [PubMed]
X. Prevention
- Preconception weight loss, dropping BMI 1 kg/m2 can prevent Gestational Diabetes
- However, weight loss during pregnancy is not recommended (risk of IUGR and SGA infants)
- Black (2022) Women Birth 35(6): 563-9 [PubMed]
XI. Resources
- AHRQ Screening and Diagnosing Gestational Diabetes
