Pregnancy

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Trauma & pregnancy

Leading non-obstetric cause of maternal morbidity and mortality. 7-24% mortality from major trauma

Increased incidence of falls and assaults

Physiological changes

Types of injury

• Splenic injury, retroperitoneal injury and haematomas and hepatic injury are more frequent. Up to 25% of pregnant women with severe blunt abdominal trauma have haemodynamically significant hepatic or splenic injuries.

• Bowel injuries are less common

• Direct fetal injuries and fractures complicate less than 1% of cases of severe blunt abdominal trauma in pregnant women. Most of these cases occur in late pregnancy and in women with significant other injuries. Fetal head injury may result from incorrect positioning of lap belt over uterus rather than over anterior iliac spines

• Before 12 weeks the small size and pelvic location of the uterus make it relatively resistant to injury. However after it becomes abdominal it is prone to injury from blunt or penetrating abdominal trauma. Perhaps more importantly women in the second and third trimesters are at increased risk of significant haemorrhage associated with uterine or pelvic trauma as a result of markedly increased uteropelvic blood flow
• 2nd & 3rd trimester bladder because intra-abdominal organ
• Assaults tend to be aimed at uterus

Uterine rupture

• uncommon
• associated with previous cesarean section and pelvic fractures
• risk factors
  • increased gestational age
  • increased force of trauma
• clinical features variable
• frequently life threatening
  • fetal mortality nearly 100%
  • maternal mortality ~10%
• repair and management of rupture per se similar to uterine rupture from other causes

Placental abruption

• forces placed on the placental-uterine interface during blunt injury, combined with the relative inelasticity of that interface, frequently result in some degree of abruption
• occurs in up to 40% of cases of severe blunt trauma and in 2-3% of cases of otherwise minor trauma, provided it is associated with deceleration and/or uterine-directed force
• classic triad only present in approx 40%
  • vaginal bleeding
  • abdominal pain
  • uterine irritability
• complications:
  • fetal: premature delivery, death
  • maternal: haemorrhage, DIC, death

Penetrating abdominal trauma

• pregant uterus may protect the other abdominal organs. Although fetal mortality is high maternal mortality is significantly lower than in non-pregant women
• pattern of injury is modified with small bowel injury being more common following upper abdominal penetrating injury than it  is in non-pregnant women

Electrical injuries

Burns

Investigations

• Necessary radiological investigations as indicated

  • Radiation hazard to fetus is unlikely but appropriate shielding should be used

• Consider possibility of uterine injury in association with pelvic fractures

• Diagnostic peritoneal lavage

  • perform through a surgical incision above fundus

• CT may miss injuries due to abdominal crowding

• Ultrasound

  • useful for assessment of abdominal injury in pregnant women

  • can accurately detect free intra-abdominal fluid, confirm gestation and fetal well-being and identify placental abnormalities but sensitivity for placental abruption only 50%

  • important to exclude herniation of abdominal contents through a ruptured diaphragm

  • pregnancy does not appear to alter sensitivity and specificity of ultrasound assessment of intra-peritoneal fluid but data very limited

• cardiotocography

  • indicated in all patients >24 weeks gestation

  • <8 contractions/hr associated with low risk of fetal or uterine injury

  • loss of beat to beat variability in fetal heart rate and (particularly late) decelerations in fetal heart rate are indicative of fetal distress and may indicate fetal or maternal injury

  • normal fetal heart rate: 120-160/min

Management

• The first priority is evaluation, resuscitation and stabilization of the mother. Most circumstances that produce maternal instability are also deleterious to the unborn fetus. Therefore, with few exceptions, treatment priorities are similar in pregnant and non-pregnant trauma victims. On presentation attention to potentially life-threatening maternal injuries should not be distracted by extensive fetal evaluation.

• Primary survey and initial resuscitation along usual lines except use lateral positioning or manual uterine displacement to avoid aortocaval compression if obviously pregnant

  • uterine blood flow is not autoregulated and may be decreased despite normal maternal haemodynamics so slight hypervolaemia is preferable to hypovolaemia. Maternal shock associated with fetal mortality of 80%

  

• After the primary survey and initial resuscitation has been completed quickly assess the size of the uterus. At 24 weeks the uterus is usually at the level of the umbilicus
  • If the uterine size does not exceed 24 weeks initial treatment should be as for a non-pregnant patient. The pregnancy is a secondary consideration
  • On the other hand, if the uterine size does exceed 24 weeks a few simple modifications have to be made to standard initial care
    • treatment of hypotension includes lateral positioning or manual uterine displacement to avoid aortocaval compression
    • The presence of a fetal heartbeat should be confirmed briefly
    • More complete fetal monitoring and evaluation should be carried out after maternal resuscitation and stabilization
    • Fetal assessment should be carried out as part of the secondary survey. As there is a significant risk of placental abruption this should be actively looked for. Ultrasound does not reliably detect placental abruption and cardiotocography is probably a better tool for risk assessment. Contractions occurring more frequently than once in every 10 minutes are associated with a 20% risk of placental abruption. Cardiotocography should be continued for a minimum of 4-6 hours and should probably be continued for 24 h in patients with frequent uterine contractions, a non-reassuring fetal heart rate pattern, vaginal bleeding, uterine tenderness and in cases of severe maternal trauma. Until cardiotocography is available monitor fetal heart rate (normal 120-160/min)
• Most authorities do not recommend the routine use of the Kleihauer-Betke test to detect the presence of fetal red blood cells in maternal blood as CTG is a more reliable tool for acute fetal evaluation. However it is useful in Rh-negative mothers in whom it is used to identify those infrequent cases in which fetomateranal haemorrhage exceeds the 30 ml for which the standard dose of anti-D immunoglobulin prevents sensitization (NB prior to 16 weeks fetus has <30 ml of blood). 10 mcg anti-D immunoglobulin required for each ml of fetal blood.
• Anti-D immune globulin 300 mcg within 72 h of injury should be considered for all Rh D negative women even if Kleihauer-Betke test negative (routinely negative if fetomaternal haemorrhage <1 ml but even these small volumes of blood sufficient to result in sensitization)
• If vasopressors required ephedrine should be first choice as it preserves uterine blood flow but there should be no hesitation in using other vasopressors when necessary
• Place chest drains slightly higher than normal (3rd or 4th interspace)
• Tetanus prophylaxis safe in pregnancy

Further reading

Van Hook JW. Clin Obs Gynae 45:414-424, 2002

©Charles Gomersall, September, 2008 unless otherwise stated. The author, editor and The Chinese University of Hong Kong take no responsibility for any adverse event resulting from the use of this webpage.
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