Gestational Diabetes

Overall: 6 to 9% of pregnant women in U.S. (2017)
1. Incidence doubled between 2006 and 2017
High risk groups (see below): 14%

Pancreatic Beta cell hyperplasia is normal in pregnancy
1. Higher Fasting and postprandial Insulin levels
Placental Hormones increase Insulin Resistance (esp. third trimester)
Gestational Diabetes results when increased beta cell function does not overcome Insulin Resistance

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
1. See Diabetes Mellitus Preconception Counseling
2. Previous abnormal lab testing
  1. Gestational Diabetes diagnosis in prior pregnancy (OR 13.2)
  2. Glucose Challenge Test (GCT)
  3. Glucose Tolerance Test (GTT)
  4. Glycosuria (Urine Glucose positive)
3. Symptoms of Diabetes Mellitus
  1. Polyuria (pre-pregnant)
  2. Polydypsia
  3. Blurred Vision
Prior Pregnancy Complication
1. History of infant with Macrosomia (OR 1.4)
  1. Weight exceeds 4000 grams or 9 pounds
2. Excessive gestational weight gain (OR 1.4)
3. History of infant with Congenital Anomaly
4. Prior Stillbirth
5. Habitual Abortions
6. Preeclampsia
7. Polyhydramnios
Ethnicity
1. Asian (RR 2.3)
2. Native American (RR 2.1)
3. Pacific Islander (RR 2.1)
4. Black (RR 1.8)
5. Hispanic (RR 1.5)
Other associated factors
1. Hypertension
2. HIV Infection
3. Polycystic Ovary Syndrome of Insulin Resistance signs (e.g. Acanthosis Nigricans)
4. Recurrent Urinary Tract Infection
5. Recurrent Vaginitis
References
1. Getahun (2010) Am J Obstet Gynecol 203(5): 467 [PubMed]

Alternative to Two step screening is a single Glucose Tolerance Test 2 hour (OGTT)
Glucose Challenge Test (GCT)
1. Non-Fasting patient drinks 50 grams of Glucose and has Serum Glucose drawn at 1 hour
2. Abnormal if Serum Glucose exceeds 130 mg/dl (some organizations use 140 mg/dl cutoff)
3. Empiric Gestational Diabetes Management for GCT >200 mg/dl (without a 3 hour GTT)
4. Timing of Test
  1. High Risk (See Risk Factors above)
    1. Test at initial Antepartum Visit to identify preexisting, undiagnosed Diabetes Mellitus (choose one)
      1. Hemoglobin A1C >=6.5% Preexisting Diabetes (>5.9% Glucose Intolerance) OR
      2. Fasting plasma Glucose >=126 mg/dl preexisting diabetes (>110 mg/dl Glucose Intolerance) OR
      3. Abnormal Glucose Tolerance Test 2 hour (OGTT)
    2. Rescreen GCT at 24-28 weeks for Gestational Diabetes if initially negative
  2. Low Risk
    1. Perform GCT at 24-28 weeks
  3. Other Indications
    1. May be considered later in pregnancy for polyhydramnios
Glucose Tolerance Test 3 hour
1. Indicated for abnormal Glucose Challenge Test
2. Fasting patient drinks 100 grams of Glucose
3. Serum Glucose drawn Fasting, 1,2, 3 hours
4. Interpretation
  1. See Glucose Tolerance Test
  2. Abnormal if 2 or more readings over respective cut-offs
  3. Thresholds for Fasting and 1, 2, and 3 hours
    1. Carpenter-Coustan (preferred): Glucose 95, 180, 155 and 140 mg/dl)
    2. NDDG (older guidelines): Glucose 105, 190, 165 and 145 mg/dl)

Fetal Macrosomia with weight > 4000 grams (RR 1.6)
1. Large for Gestational Age (LGA) >90th percentile
2. Operative delivery risk (Ceserean section)
3. 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)

Longterm risk of developing Diabetes Mellitus
1. Consider periodic Diabetes Screening, Prediabetes and lifestyle management
2. 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)

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
1. Adverse perinatal outcomes are reduced from 4% without treatment to <1% with treatment
2. Crowther (2005) N Engl J Med 352(24): 2477-86 [PubMed]
3. Metzger (2008) N Engl J Med 358(19): 1991-2002 [PubMed]

Preconception weight loss, dropping BMI 1 kg/m2 can prevent Gestational Diabetes
1. However, weight loss during pregnancy is not recommended (risk of IUGR and SGA infants)
2. Black (2022) Women Birth 35(6): 563-9 [PubMed]

AHRQ Screening and Diagnosing Gestational Diabetes
1. http://www.ncbi.nlm.nih.gov/books/NBK114844/