Trauma remains the leading cause of morbidity and mortality in pregnant women. It increases the risk of preterm delivery, placenta abruption, fetomaternal hemorrhage, and pregnancy loss. Motor Vehicle Accidents (MVAs) account for 70% of blunt abdominal trauma, then comes falls and direct assaults.
Evaluating and managing pregnant trauma patients requires knowing some physiological changes in pregnancy.
Physiological changes in pregnancy
- Maternal blood volume increases at 10 weeks and reaches a peak level at 28 weeks (45%)
- Mild anemia because of increased plasma volume (plasma > red blood cells)
- Cardiac output increases by 1-1.5L/min at 10 weeks until the end of pregnancy
- Heart rate increases by 10-20 beats/min at the 2nd trimester + decrease in the blood pressure (BP) by 10-15 mmHg. This explains the late deterioration in dropping BP; they may lose 30-40% of blood before signs of hypotension
- Uterine blood flow = maternal mean arterial pressure
- At 12 weeks, the uterus becomes an intra-abdominal organ, which is susceptible to direct injuries
- The bladder becomes anterior
- Gravid uterus causes stretching to the abdominal wall
- At 18-20 weeks, an expanding mass of gravid uterus causes hypotension in the supine position by compressing the IVC. Avoid placing IV lines in the femoral/lower extremities.
- Diaphragm elevated 4 cm, which makes the tidal volume increase by 40%, residual volume decreases by 25%, which causes the short apnea time in pregnant patients
- Splenic injury is a common cause of hemorrhage
Important actions in pregnant trauma patients
- Apply supplemental oxygen early because of compensation of hypoxia is limited
- Consider early intubation
- 50% more fluids are needed for volume replacement
- At 20 weeks, place wedge under the right hip, tilting to 30 degrees during the transfer on trauma board
- Early nasogastric tube placement to avoid aspiration
- Avoid pressors, which causes uteroplacental hypoperfusion
Rhogam (Rh immunoglobulin) and Tetanus Prophylaxis
Administer RhoD (Human Rho(D) immune globulin) to Rh-negative women; 50 mcg for <12 weeks, 300 mcg for >12 weeks. Tetanus prophylaxis is safe but considered as category C.
Images and Radiation Exposure
Do not withhold needed images. The greatest risk to fetal viability from ionizing radiation is within the first 2 weeks after conception and the highest malformation during the embryogenic organogenesis at 2-8 weeks. The risk of central nervous system teratogenesis is highest at 8-16 weeks. A dose of 5 rad is the threshold for human teratogenesis. Plain radiographs is <1 rad. Abdominal CT + Pelvic angio has the highest dose of rad (2.5-3.5). One of the critical problems is the abruption of the placenta, and CT is sensitive for abruption placenta, 86%, and has 98% specificity. The iodine contrast could cross the placenta and causing neonatal hypothyroidism.
Pelvic exam can be done only after performing an ultrasound to determine the placenta location and exclude placenta previa.
Special Tests
Vaginal fluid pH. If the pH is 7, it is amniotic fluid. If the pH is 5, it is vaginal secretions. Ferning on microscope slide = amniotic fluid.
APT ( alkali denaturation) test is qualitative evaluation to determine the presence of fetal Hg in maternal blood.
Kleihauer-Betke test measures fetal hemoglobin transfer to mothers’ blood.
Specific Issues
Fetal viability
The fetus will likely be viable at 24 weeks and above.
The normal fetal heart rate is 120-160 bpm. Heart rate below and above these limits is critical. Because ultrasound may not detect placenta abruption, nor rupture or fetal-placental injuries, high-suspicion and close monitorization are necessary.
Cardiotocography (CTG)
4-6 hours will be enough for most of the cases. Persistent contractions or uterine irritability needs an external CTG for 24 hrs. Fewer than 3 contractions per hour could indicate a safe discharge.
Indication for Emergency C-Section
- Fetal tachycardia.
- Lack of beat to beat on long term viability.
- Late deceleration = fetal distress.
C-section has a 75% survival rate in 26 weeks or above. If the fetal heartbeats are present and the procedure was performed early, the success rate is higher.
References and Further Reading
- Tintinalli, J., Stapczynski, J., Ma, O. J., Cline, D., Cydulka, R., & Meckler, G. (2010). Tintinalli’s emergency medicine: a comprehensive study guide: a comprehensive study guide. McGraw Hill Professional.
