10.2 Obstetric Hemorrhage, Placental Abruption & Preterm Labor

10.2 Obstetric Hemorrhage, Placental Abruption & Preterm Labor

Placental Abruption vs. Placenta Previa

Third-trimester vaginal bleeding is a critical obstetric emergency. The two primary causes—Placental Abruption and Placenta Previa—have distinct pathophysiological mechanisms, clinical presentations, and management mandates.

                           [ THIRD-TRIMESTER OBSTETRIC BLEEDING ]
                                             │
               ┌─────────────────────────────┴─────────────────────────────┐
               ▼                                                           ▼
    [ PLACENTAL ABRUPTION ]                                     [ PLACENTA PREVIA ]
- Premature Placental Separation                            - Placenta Implanted Over Cervical Os
- Dark Red, PAINFUL Bleeding                                - Bright Red, PAINLESS Bleeding
- RIGID, "Woody", Tender Uterus                             - SOFT, Non-Tender Uterus
- Uterine Hypertonus / Contractions                         - No Uterine Hypertonus
- Fetal Distress / Late Decelerations                       - Normal Fetal Heart Rate (Initially)
- High Risk of DIC (Tissue Factor)                          - Digital Vaginal Exam CONTRAINDICATED!

Detailed Comparison Table

---

Uterine Rupture

Uterine rupture is a catastrophic obstetric emergency involving full-thickness tearing of the uterine wall, leading to expulsion of fetal parts into the peritoneal cavity and rapid maternal-fetal exsanguination.

Risk Factors

• Prior Cesarean section delivery (especially classical vertical uterine incision).
• Trial of Labor After Cesarean (TOLAC).
• Prior myomectomy or uterine surgery.
• High parity and excessive, unmonitored oxytocin administration.
• Obstructed labor or fetal malpresentation.

Clinical Presentation & Critical Signs

1. Sudden, severe, sharp "tearing" abdominal pain occurring at the peak of a contraction.
2. Sudden cessation of uterine contractions (uterine muscle torn apart).
3. Breakthrough abdominal pain despite adequate epidural anesthesia.
4. Loss of fetal station: Presenting fetal part slips backward out of the pelvis and is no longer palpable on vaginal exam.
5. Palpable fetal parts directly beneath the maternal abdominal wall.
6. Severe fetal bradycardia or terminal late decelerations.
7. Rapid progression to maternal hypovolemic shock. Immediate surgical laparotomy and emergency delivery are mandatory.

---

Preterm Labor & Tocolytic Therapy

Preterm labor (PTL) is defined as regular uterine contractions resulting in cervical change prior to $37^{+0}$ weeks gestation. The primary objective of tocolytic therapy is not to prevent delivery indefinitely, but to delay delivery for 48 hours so that antenatal corticosteroids can be administered to accelerate fetal pulmonary maturity, and to allow safe transfer of the patient to a tertiary neonatal intensive care unit (NICU).

Tocolytic Agents in Critical Care Transport

---

Antenatal Corticosteroid Therapy

Antenatal corticosteroids are administered to all pregnant women between $24^{+0}$ and $34^{+0}$ weeks gestation who are at risk of preterm delivery within 7 days.

• Betamethasone Protocol: $12 \text{ mg}$ IM (intramuscularly) in two doses administered 24 hours apart.
• Dexamethasone Protocol: $6 \text{ mg}$ IM every 12 hours for a total of 4 doses.
• Physiological Effect: Corticosteroids cross the placenta and stimulate fetal type II pneumocytes to produce alveolar surfactant, improving lung compliance.
• Clinical Impact: Dramatically reduces the incidence and severity of neonatal Respiratory Distress Syndrome (RDS), Intraventricular Hemorrhage (IVH), Necrotizing Enterocolitis (NEC), and overall neonatal mortality.

---

Uterine Atony & Postpartum Hemorrhage (PPH)

Postpartum Hemorrhage (PPH) is historically defined as blood loss $\ge 500 \text{ mL}$ after vaginal delivery or $\ge 1000 \text{ mL}$ after C-section, but updated ACOG guidelines define PPH as cumulative blood loss $\ge 1000 \text{ mL}$ or blood loss accompanied by signs or symptoms of hypovolemia within 24 hours post-birth.

The 4 Ts of PPH Etiology

• Tone: Uterine Atony (accounts for 70–80% of all PPH cases).
• Trauma: Vaginal, cervical, or uterine lacerations.
• Tissue: Retained placenta or blood clots.
• Thrombin: Coagulopathy (pre-existing or secondary to DIC).

Stepwise Emergency Management Protocol

                        [ DIAGNOSIS OF POSTPARTUM HEMORRHAGE (PPH ≥ 1000 mL) ]
                                                   │
                                                   ▼
                                [ 1. BIMANUAL FUNDAL MASSAGE ]
                                                   │
                                                   ▼
                             [ 2. FIRST-LINE DRUG: OXYTOCIN (PITOCIN) ]
                             (10-40 units in 1L LR Infusion or 10 units IM)
                                                   │
                                                   ▼
                    ┌──────────────────────────────┴──────────────────────────────┐
                    ▼                                                             ▼
       [ PATIENT HAS HYPERTENSION? ]                                 [ PATIENT HAS ASTHMA? ]
                    │                                                             │
        ┌───────────┴───────────┐                                     ┌───────────┴───────────┐
        ▼                       ▼                                     ▼                       ▼
      YES                       NO                                  YES                       NO
(AVOID Methergine)      (Give Methergine 0.2mg IM)               (AVOID Hemabate)         (Give Hemabate 250mcg IM)
        │                       │                                     │                       │
        └───────────┬───────────┘                                     └───────────┬───────────┘
                    │                                                             │
                    └──────────────────────────────┬──────────────────────────────┘
                                                   │
                                                   ▼
                               [ 3. SECONDARY AGENTS & ANTIFIBRINOLYTIC ]
                               - Misoprostol (Cytotec) 800-1000 mcg PR
                               - Tranexamic Acid (TXA) 1 g IV over 10 min

1. Bimanual Uterine Fundal Massage: Immediately insert one gloved hand into the vagina forming a fist against the anterior uterine wall, while the external hand massages the posterior uterine fundus through the abdomen to stimulate myometrial contraction.
2. Oxytocin (Pitocin): First-line agent.
   • Dosing: Add $10–40 \text{ units}$ to $1000 \text{ mL}$ Lactated Ringer's or Normal Saline; infuse at $125–250 \text{ mL/hr}$ IV. Alternatively, give $10 \text{ units}$ IM.
   • CRITICAL SAFETY WARNING: NEVER give Oxytocin as an IV push bolus! Direct IV push causes severe vascular smooth muscle relaxation, leading to sudden hypotension, reflex tachycardia, dysrhythmias, and cardiac arrest.
3. Methylergonovine (Methergine): Ergot alkaloid.
   • Dosing: $0.2 \text{ mg}$ IM every 2–4 hours.
   • ABSOLUTE CONTRAINDICATION: Hypertension, Preeclampsia, or Eclampsia. Methergine produces intense vasoconstriction that can precipitate hypertensive emergency, stroke, or myocardial infarction.
4. Carboprost Tromethamine (Hemabate): Synthetic prostaglandin $F_{2\alpha}$.
   • Dosing: $250 \text{ mcg}$ IM (or intramyometrial) every 15–90 minutes (max total dose $2 \text{ mg}$ / 8 doses).
   • ABSOLUTE CONTRAINDICATION: Asthma. Hemabate causes potent bronchial smooth muscle constriction, resulting in severe bronchospasm and hypoxic respiratory failure.
5. Misoprostol (Cytotec): Synthetic prostaglandin $E_1$.
   • Dosing: $800–1000 \text{ mcg}$ rectally (PR) or $600 \text{ mcg}$ sublingually. Safe in hypertensive and asthmatic patients.
6. Tranexamic Acid (TXA): Antifibrinolytic agent.
   • Dosing: $1 \text{ g}$ IV in $100 \text{ mL}$ NS over 10 minutes administered within 3 hours of birth. A second $1 \text{ g}$ dose is given if bleeding continues after 30 minutes.