1.6 Hematologic, Endocrine, Connective Tissue & Other Systemic Disorders

Hematologic Disorders in Pregnancy

Physiologic Anemia vs. Pathologic Iron Deficiency

During pregnancy, maternal plasma volume expands by 45% to 50%, whereas red blood cell (RBC) erythrocyte volume increases by only 20% to 30%. This disproportionate expansion creates a state of physiologic hemodilution (physiologic anemia of pregnancy).

• Diagnostic Cutoffs for Anemia (CDC / ACOG):
  • First Trimester: Hemoglobin (Hgb) <11.0 g/dL (Hematocrit [Hct] <33%)
  • Second Trimester: Hgb <10.5 g/dL (Hct <32%)
  • Third Trimester: Hgb <11.0 g/dL (Hct <33%)
  • Postpartum: Hgb <10.0 g/dL (Hct <30%)
• Iron Deficiency Anemia (IDA): Represents 75% of all non-physiologic gestational anemias. A serum ferritin level <30 ng/mL is the single most sensitive and specific diagnostic test (microcytic, hypochromic indices with low MCV <80 fL appear later). Oral elemental iron (60–120 mg/day) paired with Vitamin C on an empty stomach is first-line; IV iron sucrose or ferric carboxymaltose is indicated for oral intolerance, severe anemia (Hgb <8–9 g/dL) late in gestation, or malabsorptive states.

Sickle Cell Disease (HbSS, HbSC, HbS-Beta Thalassemia)

Sickle cell disease is an autosomal recessive hemoglobinopathy in which an abnormal beta-globin chain causes hemoglobin S polymerisation, erythrocyte sickling, vascular occlusion, and chronic hemolytic anemia under conditions of hypoxemia, dehydration, acidosis, cold exposure, or infection.

• Maternal and Perinatal Complications: High incidence of maternal acute vaso-occlusive pain crises, acute chest syndrome (leading cause of death), preeclampsia (30%), placental infarction, fetal growth restriction (FGR), and stillbirth.
• Inpatient Crisis Management Protocol:
  1. Aggressive IV Hydration: Continuous crystalloid infusion (150–200 mL/hr) to reduce blood viscosity and reverse intravascular sickling.
  2. Oxygen Therapy: Maintain continuous pulse oximetry; administer supplemental oxygen to keep SpO2 >= 95%.
  3. Multimodal Analgesia: Prompt, scheduled or patient-controlled IV opioids (morphine, hydromorphone) for acute pain episodes.
  4. Avoid Empiric Iron Therapy: Patients with sickle cell disease receive multiple lifetime transfusions and are at high risk for hemosiderosis (iron overload). Iron supplementation is strictly withheld unless true iron deficiency is verified by low ferritin.
  5. Acute Chest Syndrome (ACS): Defined by new pulmonary infiltrates on chest X-ray accompanied by fever, chest pain, tachypnea, cough, or hypoxemia. Requires immediate ICU transfer, broad-spectrum IV antibiotics, oxygen, and emergent automated red blood cell exchange transfusion (erythrocytapheresis) to reduce HbS concentration to <30%.

+-------------------------------------------------------------------------------------------------------------------+
|                                 DIFFERENTIAL DIAGNOSIS OF THROMBOCYTOPENIA IN PREGNANCY                           |
+-------------------------------------------------------------------------------------------------------------------+
  Disorder                     Platelet Count Nadir    Onset Timing           Clinical Features & Pathophysiology
  ------------------------     --------------------    ------------           -----------------------------------
  Gestational Thrombocytopenia 70,000 - 149,000/μL     Mid-2nd to 3rd Trimester - 75% of all cases; benign hemodilution & clearance
  (GT)                         (Rarely <70,000/μL)                            - Asymptomatic; NO fetal thrombocytopenia
                                                                              - Resolves spontaneously by 2-12 wk postpartum
  -------------------------------------------------------------------------------------------------------------------
  Immune Thrombocytopenia      Often <50,000/μL        Pre-pregnancy or       - Anti-platelet IgG antibodies destroy platelets
  (ITP)                        (Can be <20,000/μL)     1st / Early 2nd Trim   - Maternal petechiae, purpura, mucosal bleeding
                                                                              - Fetal thrombocytopenia risk (IgG crosses placenta)
                                                                              - Rx: Oral Prednisone (1 mg/kg) or IVIG (1 g/kg)
  -------------------------------------------------------------------------------------------------------------------
  Preeclampsia with Severe     <100,000/μL             After 20 weeks         - Endothelial injury, platelet activation/consumption
  Features / HELLP             (Can drop <20,000)                             - Associated with severe HTN, transaminitis, hemolysis
  -------------------------------------------------------------------------------------------------------------------
  Disseminated Intravascular   Rapidly falling         Acute / Catastrophic   - Systemic consumptive coagulopathy
  Coagulation (DIC)            (often <50,000/μL)      Intrapartum/Postpartum - Prolonged PT/PTT, Fibrinogen <200, severe bleeding
+-------------------------------------------------------------------------------------------------------------------+

---

Disseminated Intravascular Coagulation (DIC) in Obstetrics

Obstetric DIC is an acute, life-threatening consumptive coagulopathy triggered by the massive release of tissue factor (thromboplastin) into the maternal circulation or by widespread endothelial disruption. Thrombin generation accelerates uncontrollably, causing systemic microvascular fibrin deposition, consumption of clotting factors and platelets, and secondary hyperfibrinolysis.

• Primary Obstetric Triggers:
  • Placental Abruption (most common cause in pregnancy due to retroplacental tissue factor release)
  • Severe Postpartum Hemorrhage (uterine atony, trauma, surgical bleeding)
  • Amniotic Fluid Embolism (AFE / Anaphylactoid Syndrome of Pregnancy)
  • Severe Pre-eclampsia and HELLP Syndrome
  • Intra-amniotic Infection / Sepsis (gram-negative endotoxins)
  • Retained Dead Fetus Syndrome (prolonged retention >4–6 weeks)

Diagnostic Laboratory Profile and Transfusion Component Therapy

+-------------------------------------------------------------------------------------------------------------------+
|                                 OBSTETRIC DIC: LABORATORY TARGETS & COMPONENT THERAPY                             |
+-------------------------------------------------------------------------------------------------------------------+
  Laboratory Test         Normal Third Trimester Value     DIC Diagnostic Threshold     Component Therapy / Target
  ---------------         ----------------------------     ------------------------     --------------------------
  Fibrinogen              350 - 600 mg/dL (Hyperfibrin)    <200 mg/dL (Critical: <100)  CRYOPRECIPITATE (1-2 pools)
                                                                                        Target: >150 - 200 mg/dL
  -------------------------------------------------------------------------------------------------------------------
  Platelet Count          150,000 - 400,000/μL             <100,000/μL                  PLATELETS (1 apheresis unit)
                                                                                        Target: >50,000/μL
  -------------------------------------------------------------------------------------------------------------------
  Prothrombin Time (PT)   10 - 12 seconds                  Prolonged (>1.5x control)    FRESH FROZEN PLASMA (FFP)
  aPTT                    25 - 35 seconds                  Prolonged (>1.5x control)    Target: Normal PT/INR & aPTT
  -------------------------------------------------------------------------------------------------------------------
  D-Dimer                 Mildly elevated in pregnancy     Markedly Elevated (>5-10x)   Reflects active fibrinolysis
  -------------------------------------------------------------------------------------------------------------------
  Hemoglobin / Hct        11 - 14 g/dL / 33 - 42%          Acute drop                   PACKED RED BLOOD CELLS (PRBCs)
                                                                                        Target: Hgb >8.0 g/dL
+-------------------------------------------------------------------------------------------------------------------+

• Cryoprecipitate: The primary source of concentrated fibrinogen (contains 200–250 mg fibrinogen per unit, plus Factor VIII, von Willebrand factor, and Factor XIII). A 10-unit pool raises maternal fibrinogen by approximately 50 to 100 mg/dL.
• Tranexamic Acid (TXA): Antifibrinolytic agent administered as 1 g IV over 10 minutes within 3 hours of bleeding onset for postpartum hemorrhage.

---

Maternal Endocrine Disorders

Thyroid Disease in Pregnancy

• Physiologic Adaptations: Human chorionic gonadotropin (hCG) shares structural homology with TSH, weakly stimulating the thyroid gland in the first trimester, causing a transient decrease in TSH. Estrogen increases Thyroid-Binding Globulin (TBG) 2-fold, increasing total T3 and T4, while free T4 remains in the normal reference range.
• Hypothyroidism (Hashimoto's Thyroiditis):
  • Clinical Impact: Inadequate maternal thyroid hormone during the first trimester impairs fetal neurodevelopment, causing reduced offspring IQ, preeclampsia, abruption, and low birth weight.
  • Treatment: Levothyroxine (Synthroid): Dosing must be increased by 25% to 30% immediately upon pregnancy confirmation. Target TSH: <2.5 mIU/L in 1st trimester, <3.0 mIU/L in 2nd/3rd trimesters. Monitor TSH every 4 to 6 weeks.
• Hyperthyroidism (Graves' Disease):
  • Antithyroid Drug Selection: Propylthiouracil (PTU) is used during the first trimester because Methimazole is associated with specific embryopathies (aplasia cutis congenita, choanal atresia, and esophageal atresia). Methimazole is substituted during the second and third trimesters to avoid PTU-associated maternal fulminant hepatic necrosis.
  • Thyroid Storm: Life-threatening hypermetabolic emergency triggered by labor, infection, or cesarean birth. Symptoms: hyperthermia (>103°F / 39.4°C), tachycardia (>140 bpm), atrial fibrillation, agitation, and congestive heart failure. Treatment: 1) High-dose PTU (600–800 mg PO/NG); 2) Saturated Solution of Potassium Iodide (SSKI) given 1 hour AFTER PTU; 3) IV Dexamethasone (2 mg q6h) to block T4 to T3 conversion; 4) IV Propranolol for beta-blockade; 5) Supportive cooling.

---

Autoimmune Connective Tissue Disorders: Systemic Lupus Erythematosus (SLE)

Systemic Lupus Erythematosus (SLE) is an autoimmune disorder characterized by antinuclear antibody (ANA) production, immune complex deposition, and multiorgan inflammation.

Lupus Flare vs. Preeclampsia Differentiation

Both disorders present in late pregnancy with hypertension, proteinuria, and renal decline. Differentiating features include:

• Lupus Nephritis Flare: Decreased serum complement levels (low C3 and C4), elevated anti-dsDNA antibody titers, and active urinary sediment (dysmorphic red blood cells and RBC casts).
• Preeclampsia: Serum complement levels (C3/C4) remain normal or elevated, anti-dsDNA is negative, and urine sediment shows proteinuria without cellular casts.

Neonatal Lupus and Congenital Complete Heart Block

Maternal IgG autoantibodies directed against ribonucleoprotein antigens—specifically anti-SSA/Ro and anti-SSB/La—cross the placenta starting at 16 weeks of gestation. These antibodies bind to fetal cardiac conduction tissue, triggering autoimmune myocarditis, inflammatory destruction, and irreversible fibrosis of the fetal atrioventricular (AV) node.

• Clinical Manifestation: Irreversible Congenital Third-Degree (Complete) Heart Block developing between 16 and 26 weeks of gestation. The fetal heart rate baseline becomes permanently bradycardic at 50 to 80 beats per minute, unresponsive to movement or contractions.
• Inpatient Intrapartum Monitoring: Electronic fetal heart rate monitoring will demonstrate persistent fixed bradycardia without variability. Immediate delivery room pediatric cardiology resuscitation with external/temporary transvenous pacing capability is mandatory.

---

Hyperemesis Gravidarum and Bariatric Surgery Considerations

Hyperemesis Gravidarum (HG)

• Definition: Severe, intractable nausea and vomiting leading to >5% pre-pregnancy weight loss, dehydration, ketonuria, and electrolyte derangements (hypokalemic, hypochloremic metabolic alkalosis).
• Wernicke's Encephalopathy Prevention: Prolonged vomiting and carbohydrate metabolism deplete maternal thiamine (Vitamin B1). Thiamine (100 mg IV) MUST ALWAYS BE ADMINISTERED BEFORE any dextrose-containing IV solutions to prevent acute Wernicke's encephalopathy (confusion, ataxia, nystagmus/ophthalmoplegia, and permanent memory loss).

Post-Bariatric Surgery in Inpatient Obstetrics

• Roux-en-Y Gastric Bypass / Malabsorptive Procedures: High risk of maternal micronutrient deficiencies (Vitamin B12, folate, iron, Vitamin D, calcium, copper, and fat-soluble vitamins).
• Dumping Syndrome: Ingestion of concentrated simple carbohydrates triggers rapid fluid shifts into the bowel (early dumping) and severe reactive hyperinsulinemic hypoglycemia (late dumping). The standard 50g oral Glucose Loading Test (GLT) is strictly avoided in post-gastric bypass patients due to severe dumping; gestational diabetes screening is performed using home fasting and 1- to 2-hour postprandial capillary glucose logs for 1 to 2 weeks.
• Internal Hernia: Acute abdominal pain in a pregnant post-bariatric patient is an acute surgical emergency representing internal bowel herniation behind mesenteric surgical defects, which can rapidly progress to strangulation and bowel necrosis.