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Pregnancy is a diabetogenic state because of:

  1. Insulin resistance
    1. Production of HPL
    2. Increased production of cortisol, estrogen, and progesterone
    3. Increased destruction of insulin by kidneys and placenta
  2. Increased lipolysis
  3. Altered gluconeogenesis

Effects of Pregnancy on Diabetes

  1. Increased insulin requirement
  2. Progression of diabetic retinopathy
  3. Worsening of diabetic nephropathy
  4. Worsening of diabetic cardiomyopathy
  5. Hypoglycemia

Effects of Diabetes on Pregnancy


Maternal Effects

  1. Increased risk of preeclampsia, polyhydramnios and preterm labor
  2. Higher risk of infection
  3. PPH
  4. Operative delivery

Fetal Effects

  1. Recurrent first trimester abortions
  2. Congenital anomalies
  3. Sudden IUFD at term
  4. Macrosomia (ACOG definition: birthweight >4.5 kg)
  5. Shoulder dystocia. With birthweight remaining same, the babies of diabetic mothers are more prone to develop shoulder dystocia compared to babies of nondiabetic mothers

Neonatal effects

  1. Hyaline Membrane Disease/Respiratory Distress Syndrome
  2. Hyperviscosity syndrome
  3. Genetic transmission (infants of mothers with type I diabetes have a 4-5% risk of acquiring diabetes; infants of mothers with type II diabetes have a 25-50% risk of diabetes)
  4. Hypoglycemia/hypocalcemia

White's Classification of Diabetes Complicating Pregnancy



Fasting Plasma Glucose

2-h Postprandial Glucose









 >120 mg/dL




Age of Onset (year)

Duration (year)

Vascular Disease








 Over 20


 Before 10












 Benign retinopathy


 Proliferative retinopathy









High Risk Groups

  1. Elderly (age >35 years)
  2. BOH
  3. Previous unexplained fetal demise
  4. Previous macrosomic baby
  5. Family history of DM
  6. Past history of GDM
  7. Repeated infections especially candidiasis
  8. Previous anomalous baby
  9. Obesity

O'Sullivan Blood Sugar Screening Test (Glucose Challenge Test)

  1. The ideal time to do this test is 24-28 weeks of gestation (as insulin resistance in pregnancy is maximum at 28 weeks of gestation).
  2. 50 g glucose is given irrespective of the period of fasting and plasma glucose is measured after 1 h. If it is >140 fig/ dL it is an indication for further testing.
  3. RBS >200 mg/dL or FBS >125 mg/dL indicates overt OM and there is no need to do GTI
  4. Glycosylated Hb (HbA1C): <8%= minimal risk of anomalies/ abortions and >9% = poor glycemic control and increased risk of anomalies/ abortions

Confirmatory Tests

Glucose Tolerance Test (GTT) (upper limit of normal during pregnancy)


Glucose Load (g)

FBS (mg/dL)

1 h (mg/dL)

2 h (mg/dL)

3 h (mg/dL)


Carpenter / Coustan

National Diabetes Data Group















NOTE: ACOG also recommends 100 g glucose load for CTT. If 2 or more values are abnormal, patient has gestational diabetes.

Congenital Malformations in Infants of Diabetic Mothers

MC anomaly = neural tube defects (anencephaly and spina bifida) followed by cardiac anomalies


Most specific anomaly = caudal regression syndrome/sacral agenesis

  1. Central Nervous System
    1. Anencephaly and spina bifida
    2. Encephalocele
    3. Meningomyelocele and holoprosencephaly
    4. Microcephaly
  2. Cardiovascular
    1. Transposition of the great vessels
    2. Ventricular septal defect and atrial septal defect
    3. Hypoplastic left ventricle
    4. HOCM
      NOTE: VSD is the MC cardiac anomaly, TGV is the most specific cardiac anomaly in infants of diabetic mothers
  3. Skeletal
    1. Caudal regression syndrome (sacral agenesis)
  4. Genitourinary
    1. Absent kidneys
    2. Polycystic kidneys
    3. Double ureter
  5. Gastrointestinal
    • Tracheoesophageal fistula
    • Bowel atresia
    • Imperforate anus

Pederson's Hypothesis

Maternal hyperglycemia causes fetal hyperglycemia, which, in turn, causes fetal hyperinsulinemia and leads to fetal microsomy



  1. Insulin is the drug of choice for management of DM/GDM in pregnancy (insulin does not cross the placenta).
  2. Indication for starting insulin in pregnancy:
  3. If FBS is more than 96-108 mg/ dL or if PLBS is more than 125 mg/ dL with diabetic diet, then insulin has to be started in pregnancy.
  4. Oral hypoglycemic agents are contraindicated, since they cross the placenta and can lead to fetal hypoglycemic episodes and ear anomalies.
  5. Lung maturity is delayed in DM/GDM.
  6. L/S >2:1 is not reliable.
  7. Phosphatidyl glycerol in amniotic fluid is 100% confirmatory of lung maturity in these cases.
  8. Patients with GDM/DM should be delivered between 38 and 39 weeks of gestation, as there is a risk of sudden IUFD at full term.
  9. ACOG recommends elective LSCS if fetal weight is more than 4.5 kg in a DM patient and more than 5 kg in a non-DM patient.
  10. Fifty percent of GDM patients will develop overt diabetes in future.

NOTE: Hormones which do not cross the placenta are

  1. Insulin
  2. PTH
  3. Calcitonin

Cardiovascular Disease In Pregnancy

Clarke's Classification for Risk of Maternal Mortality Caused by Various Heart Diseases


Cardiac Disorder

Mortality (%) 1

Group 1-minimal risk


Atrial septal defect


Ventricular septal defect


Patent ductus arteriosus


Pulmonic or tricuspid disease


Fallot tetralogy, corrected


Bioprosthetic valve


Mitral stenosis, NYHA classes 1 and 2


Group 2-moderate risk


Mitral stenosis, NYHA classes ill and IV


Aortic stenosis


Aortic coarctation without valvular involvement


Fallot tetralogy, uncorrected


Previous myocardial infarction


Marfan syndrome, normal aorta


Mitral stenosis with atrial fibrillation


Artificial valve


Group 3-major risk


Pulmonary hypertension(primary and secondary)


Aortic coarctation with valvular involvement


Marfan syndrome with aortic involvement


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