12.4 Anemia in Pregnancy & Gestational Diabetes Mellitus

12.4 Anemia in Pregnancy & Gestational Diabetes Mellitus

Medical disorders complicating pregnancy contribute substantially to indirect maternal mortality and long-term perinatal morbidity. Anemia and Gestational Diabetes Mellitus (GDM) represent the two most common medical conditions encountered in obstetric practice in India.

---

1. Anemia in Pregnancy

Physiological Anemia of Pregnancy

During pregnancy, maternal plasma volume expands by 40–50%, whereas red blood cell (RBC) mass increases by only 20–30%. This disproportionate hemodilution results in a physiological drop in hemoglobin concentration and hematocrit, reaching its nadir at 28–32 weeks of gestation.

Diagnostic Cut-offs & Severity Grading

• WHO Diagnostic Criterion: Hemoglobin (Hb) $< 11.0\text{ g/dL}$ (or Hematocrit $< 33\text{ %}$) in the 1st and 3rd trimesters, and $< 10.5\text{ g/dL}$ in the 2nd trimester.
• ICMR / Anemia Mukt Bharat Severity Grading:
  • Mild Anemia: Hb 10.0 – 10.9 g/dL
  • Moderate Anemia: Hb 7.0 – 9.9 g/dL
  • Severe Anemia: Hb 4.0 – 6.9 g/dL
  • Very Severe Anemia: Hb $< 4.0\text{ g/dL}$ (high risk of high-output congestive heart failure and maternal mortality!)

Iron Deficiency Anemia (IDA)

Iron Deficiency Anemia accounts for $> 85\text{ %}$ of all anemia cases in pregnancy.

• Laboratory Evaluation:
  • Peripheral Blood Smear: Microcytic, hypochromic red cells with anisopoikilocytosis.
  • Red Cell Indices: Reduced MCV ($< 80\text{ fL}$), reduced MCH ($< 27\text{ pg}$), elevated RDW ($> 15\text{ %}$).
  • Serum Ferritin: $< 30\text{ ng/mL}$ (the single most sensitive and specific biochemical marker for early iron deficiency).
  • Serum Iron & TIBC: Decreased serum iron ($< 60\text{ mcg/dL}$), elevated Total Iron Binding Capacity (TIBC $> 400\text{ mcg/dL}$), transferrin saturation $< 16\text{ %}$.

Treatment Protocols & Iron Dose Calculations

1. Oral Iron Therapy: Indicated for mild anemia and early moderate anemia ($> 14\text{ weeks}$). Administer 100–200 mg elemental iron daily along with $1\text{ mg}$ folic acid. Reticulocyte response peaks at 7–10 days; Hb rises by $0.7–1.0\text{ g/dL}$ per week.
2. Parenteral Iron (IV Iron Sucrose / Ferric Carboxymaltose - FCM): Indicated for moderate anemia (Hb $7–9.9\text{ g/dL}$) beyond 16–24 weeks, oral iron intolerance, severe non-compliance, or malabsorption.
   • Ganzoni Formula for Total Iron Deficit: $\text{Total Iron Deficit (mg)} = \text{Weight (kg)} \times \left( \text{Target Hb} - \text{Actual Hb} [\text{g/dL}] \right) \times 2.4 + \text{Depot Iron (500 mg)}$ (Target Hb is typically taken as $11.0\text{ g/dL}$ or $12.0\text{ g/dL}$).
3. Blood Transfusion (Packed Red Blood Cells / PRBC):
   • Indications:
     • Severe anemia (Hb $< 7\text{ g/dL}$) diagnosed after 36 weeks of gestation (insufficient time for parenteral iron to take effect before labor).
     • Severe anemia (Hb $< 5\text{ g/dL}$) at any gestational age.
     • Anemia complicated by cardiac failure, severe infection, or active bleeding.

---

2. Gestational Diabetes Mellitus (GDM)

Gestational Diabetes Mellitus is defined as carbohydrate intolerance of variable severity with onset or first recognition during pregnancy.

Diabetogenic Pathophysiology of Pregnancy

Pregnancy is a diabetogenic state. The placenta secretes human Placental Lactogen (hPL), Human Placental Growth Hormone, Cortisol, Progesterone, and Prolactin. These hormones act as insulin antagonists, inducing progressive maternal peripheral insulin resistance. Peak insulin resistance occurs between 24 and 28 weeks of gestation.

DIPSI Guidelines for Screening & Diagnosis (Single-Step Test)

The Diabetes in Pregnancy Study Group India (DIPSI) guidelines provide a non-fasting, single-step diagnostic procedure tailored for resource-limited settings:

• Procedure: 75 g oral anhydrous glucose dissolved in 300 mL of water is administered to the pregnant woman regardless of the time of her last meal or fasting status.
• Timing of Blood Sample: Venous plasma glucose is measured at 2 hours.

WHO / IADPAG 75g OGTT Criteria (Fasting Required)

Alternative 2-hour 75g Oral Glucose Tolerance Test requiring an 8-hour overnight fast:

• Fasting: $\ge 92\text{ mg/dL}$
• 1-Hour: $\ge 180\text{ mg/dL}$
• 2-Hour: $\ge 153\text{ mg/dL}$ (Any ONE abnormal value confirms GDM).

Maternal, Fetal & Neonatal Complications

[Maternal Hyperglycemia] -> [Glucose Crosses Placenta (Insulin Does NOT)]
                                      |
                                      v
                      [Fetal Hyperglycemia & Hyperinsulinemia]
                                      |
     +-------------------+------------+------------+-------------------+
     |                   |                         |                   |
     v                   v                         v                   v
[Fetal Macrosomia]  [Inhibition of]       [Polycythemia &]      [Neonatal]
(Weight > 4 kg,      Surfactant           Hyperbilirubinemia   [Hypoglycemia]
 Shoulder Dystocia)  (Neonatal RDS)                            (Post-clamping)

• Maternal Complications: Pre-eclampsia (2x risk), Polyhydramnios (due to fetal osmotic diuresis), operative delivery (Cesarean section / instrumental), soft tissue trauma, 50% lifetime risk of developing Type 2 Diabetes Mellitus within 10–15 years.
• Fetal Complications:
  • Fetal Macrosomia: Birth weight $> 4.0\text{ kg}$ or $> 90^{\text{th}}$ percentile (hyperinsulinemia acts as growth hormone).
  • Shoulder Dystocia: Deposition of fat around fetal shoulders and chest.
  • Congenital Anomalies: Seen in pre-gestational diabetes (not pure GDM). Caudal Regression Syndrome (Sacral Agenesis) is the most specific anomaly. Cardiac defects (Transposition of Great Arteries, VSD) are most common overall.
• Neonatal Complications:
  • Neonatal Hypoglycemia: Defined as blood glucose $< 40\text{ mg/dL}$. Sudden cessation of maternal glucose supply at cord clamping while fetal hyperinsulinemia persists.
  • Respiratory Distress Syndrome (RDS): Fetal hyperinsulinemia inhibits cortisol-mediated synthesis of pulmonary surfactant (dipalmitoylphosphatidylcholine).
  • Neonatal Hypocalcemia, Hypomagnesemia, Polycythemia, and Hyperbilirubinemia.

Glycemic Targets & Management

1. Medical Nutrition Therapy (MNT): First-line treatment for 2 weeks. Caloric distribution: 30–35 kcal/kg/day (45–55% complex carbs, 20% protein, 30% fat).
2. Target Blood Glucose Levels (ACOG / DIPSI):
   • Fasting Blood Glucose: $< 95\text{ mg/dL}$ (5.3 mmol/L)
   • 1-Hour Postprandial: $< 140\text{ mg/dL}$ (7.8 mmol/L)
   • 2-Hour Postprandial: $< 120\text{ mg/dL}$ (6.7 mmol/L)
   • HbA1c: $< 6.0\text{ %}$
3. Pharmacotherapy: If MNT fails to achieve blood glucose targets after 2 weeks.
   • Insulin: Gold standard drug of choice. Does not cross the placenta. Total starting dose: 0.7–1.0 U/kg/day.
   • Metformin: Approved oral alternative if patient refuses insulin or compliance is questionable. Crosses placenta but safe.