Trauma and pregnancy

Anatomical and Physiological Alterations

• Anatomical:
  • Alterations of Uterus Position:
    • First 12 weeks: Remain a pelvic organ
    • At 12 weeks: Begins to rise out of pelvis
    • By 20 weeks: At umbilicus
    • By 34-36 weeks: Reaches costal margin
  • Bowel pushed cephalad into upper abdomen
    • In blunt trauma, bowel more protected than uterus
    • Position of spleen and liver unchanged
  • Amniotic fluid
    • Generous amount surrounds foetus in 2nd trimester
    • Amniotic fluid embolism and DIC possible if fluid gains access to maternal intravascular space
  • Pelvic fractures
    • In late gestation, may result in skull fracture or serious intra-cranial injury to foetus
    • Large engorged pelvic vessels that surround uterus can contribute to massive retroperitoneal bleeding after blunt trauma
  • Placenta
    • Little elastic tissue
    • Vulnerable to shear forces which may be vulnerable to Placental Abruption
• Physiological Alterations
  • Blood volume and composition
    • Plasma volume increases but RBC volume has a smaller increase
      • Thus, develops physiologic anaemia of pregnancy
    • Pregnant pts can lose 1200 to 1500ml of blood before exhibiting signs and symptoms of hypovolaemia
    • WCC increases
    • Clotting factors and fibrinogen mildly elevated
  • Haemodynamics
    • Cardiac output – increases after 10th week because of increase plasma volume and decrease in vascular resistance of uterus and placenta
      • In supine position, IVC compression can decrease cardiac output by 30%
    • Heart rate increases 10-15 bpm
    • Blood pressure 5-15 mmHg fall in systolic and diastolic BP during 2nd trimester
    • Returns to near-normal at term
    • ECG changes: Axis may shift leftward by 15 degrees, flattened or inverted T-waves in leads 3 and aVF and precordial leads normal, increase in ectopic beats
  • Respiratory system
    • Minute ventilation increases as a result of increase in tidal volume
    • Hypocapnia (PaCO2 of 30 mmHg) common in late pregnancy
    • Thus, normocapnia may indicate impending respiratory failure
    • Diaphragmatic elevation reduces residual volume
    • Oxygen consumption increased
  • GI system
    • Delayed gastric emptying
      • Thus, early NG Tube should be considered
  • Urinary system
    • GFR and renal blood flow increase
    • Serum creatinine and urea nitrogen fall
    • Glycosuria common
  • MSK
    • Pubic symphysis widens to 4-8mm
    • Sacroiliac joint space increases
  • Neurological system
    • Eclampsia can mimic head injury
      • Consider if seizures occur with: HTN, hyper-reflexia, proteinuria and peripheral oedema

Unique Risks to Pregnancy Pts

• Blunt trauma:
  • Risk of uterine rupture and placental rupture
• Penetrating trauma:
  • Risk to abdominal viscera low but risk to foetus high

Primary Survey on Pregnant Women

• Early consultation with obstetrics
• Manual displacement of uterus to the left
• Early crystalloid fluid resuscitation and blood administration to support physiological hypervolaemia of pregnancy
• Vasopressors last resort – reduces uterine blood flow resulting in foetal hypoxia
• Check fibrinogen level – normal level may indicate early DIC
• Check for Placental Abruption: Vaginal bleeding, uterine tenderness, frequent uterine contractions, uterine tetany and uterine irritability
• Check for Uterine Rupture: Abdominal tenderness, guarding, rigidity, rebound tenderness
• Continuous foetal monitoring with tocodynamometer should be performed beyond 20-24 weeks gestation
• Indicated radiographic studies should be performed – benefits outweigh risks
• All pregnant Rh-negative trauma pts should receive Rh immunoglobulin therapy unless injury remove from uterus, e.g. isolated distal extremity – should be given within 72 hours