Trauma in Pregnancy

1. THE 2-MINUTE PHYSIOLOGY (Rapid Pathophysiology)

• The Core Mechanism: The physiologic response of a pregnant trauma patient is uniquely altered by vast shifts in maternal cardiovascular tone and plasma volume, which increases by 50%.
• Caval Compression: In the supine position, the gravid uterus can compress the inferior vena cava as early as 18 weeks of gestation. This mechanical obstruction severely impedes venous return, rapidly decreasing maternal cardiac output by up to 30%.
• The Shearing Effect: Placental abruption occurs when the inelastic placenta shears away from the highly elastic uterus. This can be triggered purely by sudden deceleration forces, meaning catastrophic abruption can occur with little to no direct external trauma to the abdominal wall.
• Fetal Hypoperfusion: Because maternal compensation for hypoxia is limited, hypovolemia and hypoxemia rapidly exacerbate fetal hypoperfusion, making maternal mortality the most common cause of fetal mortality.

2. THE BEDSIDE ACTION PLAN (Rapid ER Management)

• Maternal Priority: The sequence of trauma care is the same as for nonpregnant patients; effective resuscitation of the mother is the absolute best method to save the fetus.
• Positioning: Immediately perform left-uterine displacement (LUD) for any patient >20 weeks gestation. Place a wedge or rolled blanket under the right side of the spine board, tilting the entire patient approximately 30 degrees to the left to prevent caval compression.
• Airway & Breathing: Administer supplemental oxygen to maintain a pulse oximetry strictly >95%, and consider early endotracheal intubation, as compensation for hypoxia is highly limited in pregnancy.
• Circulation & Access: Establish two large-bore IVs or IO access strictly above the diaphragm. Avoid placing IV lines in the lower extremities or femoral region due to IVC compression and the risk of infusing into injured pelvic veins.
• Resuscitation Goals: Increase the standard crystalloid infusion volume by 50% to account for the expanded maternal plasma volume. Do not administer vasopressors until volume and blood are fully replaced to prevent iatrogenic uteroplacental hypoperfusion.
• Procedural Modifications: If a chest tube is required, placement should be moved cephalad due to the anatomic elevation of the diaphragm by the gravid uterus.

3. THE DIAGNOSTIC GRID (Differential Diagnosis & Workup)

• Critical Mimics & Complications: Placental abruption, uterine rupture, premature rupture of membranes, and fetal-maternal hemorrhage. Always screen women of childbearing age for intimate partner violence (IPV).
• Prioritized Diagnostic Workup:
• Obstetric Labs: Immediately obtain blood for Type and Cross-match, checking maternal Rh status. Order a Kleihauer-Betke test or flow cytometry to quantify fetal-maternal hemorrhage.
• Coagulation Panel: Send a complete blood count (CBC), prothrombin time (PT), partial thromboplastin time (PTT), fibrinogen, and D-dimer or fibrin degradation products to monitor for coagulopathy triggered by abruption or hemorrhage.
• Continuous Monitoring: Initiate continuous cardiotocographic (CTG) and fetal heart rate monitoring for a minimum of 4 to 6 hours for all viable pregnancies to evaluate for occult fetal distress or preterm labor.

4. THE VISUAL BOARD (ECG / POCUS / Imaging)

• The Fetal FAST Exam: Perform the eFAST contemporaneously with the primary survey. Transition the machine to obstetric settings to evaluate the Fetal FAST components: Number of fetuses, Presentation (cephalic/breech/transverse), Placentation (low/fundal/anterior/posterior), Amniotic fluid volume, Cardiac activity, and Femur length. A femur length >4 cm indicates a viable fetus.
• Placental Ultrasound: Ultrasound is essential to visualize placental abruption and differentiate it from placenta previa, though abruption remains primarily a clinical diagnosis.
• Radiography Principles: Do not withhold or delay necessary imaging out of fear of fetal radiation exposure; prioritize the optimal resuscitation of the mother and obtain CT/X-rays as clinically indicated.

5. THE SCORING MATRIX (Risk Stratification & Guidelines)

• The Viability Landmark: A uterine fundus palpable at or above the umbilicus correlates with >20 weeks gestation, serving as the clinical threshold for fetal viability and the indication for resuscitative cesarean delivery.
• The 4-Hour Rule: For pregnant patients involved in mild blunt trauma, maternal vital signs do not reliably predict fetal outcome. Therefore, guidelines mandate a minimum of 4 hours of cardiotocographic monitoring to predict fetal outcome and identify occult distress.

6. THE DANGER ZONE (Pitfalls & Critical Actions)

• The Supine Pitfall: Leaving a pregnant trauma patient flat on their back is a catastrophic error that drops cardiac output by 30%. Critical Action: Always manually displace the uterus or tilt the patient to the left.
• The Premature Closure Trap: Assuming the fetus is unharmed because the mother was in a "low-speed" collision and has normal vital signs. Critical Action: Abruption can occur without abdominal pain or severe external trauma; mandatory 4-hour CTG monitoring is required.
• The Resuscitative Hysterotomy Action: In the event of maternal cardiac arrest in a pregnancy >20 weeks, an emergent resuscitative cesarean delivery (vertical midline incision) must be initiated within 4 minutes of loss of pulse, with fetal delivery completed by 5 minutes. Do not waste time attempting to obtain fetal heart tones or ultrasound prior to cutting.

7. MCQ MASTERCLASS (Written Exam Tips)

• High-Yield "Buzzword": "Inelastic placenta shears away from elastic uterus" -> indicates Placental Abruption.
• Exam Distractor: A question asks what is the best predictor of fetal outcome after a minor blunt trauma. Distractor options will include "maternal vital signs" or "ultrasound." Correction: The only correct answer is "cardiotocographic monitoring for 4 hours".
• Procedural Distractor: A question describes placing an IV in the saphenous or femoral vein of a pregnant trauma patient. Correction: Intravenous access must be established strictly above the diaphragm.
• Pharmacology Fact: All Rh-negative pregnant trauma patients must be administered Rh immune globulin (RhoGAM) within 72 hours of the injury.

8. THE BOARDROOM SCRIPT (OSCE & Oral Board Tips)

"Examiner, I am evaluating a female trauma patient. I will immediately ascertain her pregnancy status. Noting her uterine fundus is above the umbilicus, indicating >20 weeks gestation, I will apply a wedge to tilt the backboard 30 degrees to the left to prevent caval compression and optimize maternal cardiac output. I am establishing two large-bore IVs exclusively above the diaphragm and increasing my standard crystalloid fluid resuscitation by 50% to account for her expanded plasma volume. While prioritizing the maternal ATLS primary survey, I am concurrently performing a Fetal FAST to check cardiac activity and femur length. I am ordering a type and cross to check Rh status, a Kleihauer-Betke test, and a coagulation panel. I will consult obstetrics immediately to initiate continuous cardiotocographic monitoring for a minimum of 4 hours to rule out occult placental abruption.".