Trauma during pregnancy is the leading non-obstetric cause for maternal morbidity and mortality, occurring in 8 per cent of all pregnancies.1 Furthermore, there are significant potential risks to the fetus, including intrauterine fetal demise, fetal injury (traumatic, cerebral palsy), preterm labour, placental abruption and uterine rupture as a result of a maternal injury. Approximately 50 per cent of trauma in pregnancy is due to motor vehicle accidents, while the remainder is the result of domestic/intimate partner violence, falls and burns. While most trauma during pregnancy in Australia relates to blunt trauma, penetrative injury (knife or gunshot wounds) present a greater risk given the gravid uterus is the most likely abdominal organ to be injured, and results in a higher perinatal mortality of up to 70 per cent.2 Fortunately, major trauma remains relatively uncommon in the experience of most obstetricians. However, it is important to have established clinical skills and protocols for optimal care to improve outcomes for mothers and their babies in the event of trauma.
Primary survey/initial assessment
The first priority always remains the assessment of the woman and treatment of her life-threatening injuries which, in effect, will improve the fetal outcomes. Her initial assessment and resuscitation should be in accordance with the Advanced Trauma Life Support Guidelines (ATLS), with consideration of obtaining an adequate airway, ventilation and haemodynamic stabilisation. Avoidance of hypoxia, hypotension, acidosis and hypothermia in the woman will improve uteroplacental flow and therefore limit further fetal injury.
However, there are additional considerations in pregnancy that need to be addressed when performing a primary survey and in the initial management of the woman:
- It requires an understanding of the altered anatomy and physiology of a pregnant patient that allows better identification of a patient at risk. These changes can mask or mimic injury, potentially resulting in misinterpretation and inappropriate management.
- It is important to position the woman after 20 weeks gestation in left lateral tilt (~300)or alternately manually displace the uterus (possible even with spinal precautions) to prevent aortocaval compression.
- It is important not to withhold medications, treatment, procedures or investigations necessary to treat the mother out of concern for the pregnancy.
- Consider treatment of pregnant trauma patients (especially those after 20 weeks) at a hospital with a combined trauma and obstetric service, if at all possible.
- If in cardiac arrest, it is important that defibrillation and advanced cardiac life support are provided as per a nonpregnant patient, but with consideration of a perimortem caesarean section (if thought to be more than 20 weeks gestation) if there is no effective response to CPR within four minutes, with the aim to delivery by five minutes.
Once stabilised, secondary evaluation for maternal and fetal injury should occur simultaneously. This begins with a thorough history, including mechanism of trauma, obstetric and antenatal history, and assessment of gestational age, if known. History specific to complications of trauma in a pregnant patient include vaginal bleeding or loss of liquor, abdominal pain or contractions and maternal perception of fetal movements.
Specific considerations on examination include:
- Abdominal palpation to confirm fetal presentation, assessment of uterus for tone, contractions and tenderness, noting that the clinical signs of peritoneal irritation are less pronounced in pregnancy
- Vaginal speculum examination, where indicated, to exclude cervical effacement and dilation, vaginal bleeding and ruptured membranes
- For viable gestations after 24 weeks, a cardiotocography (CTG) should be performed to assess fetal wellbeing and uterine activity
Diagnostic radiologic imaging
Clinician and patient concern regarding the risks of ionising radiation are often disproportionate to the actual risk.3 At radiation doses of <50mGy, there is no increased risk of pregnancy loss, fetal anomalies, growth restriction, intellectual disability or fetal anomalies. In addition, the lifetime carcinogenic effects of in utero ionising radiation exposure are thought to be small (<0.8% for <20mGy, 2% <50mGy)4 The majority of diagnostic imaging (chest, abdominal, pelvic x-rays, head CT) are associated with fetal doses comfortably below this level, with abdominal and pelvic CT imaging involving a slightly higher fetal radiation dose at approximately 20–35mGy. If diagnostic radiologic imaging is indicated after maternal trauma, it should not be precluded due to concerns about fetal exposure.
Where possible, women should be counselled about the risks of in utero radiation exposure as above, and the risks must be weighed against the potential of identifying or excluding life-threatening injuries with imaging. Greater fetal radiation exposure occurs with direct abdominal/pelvic imaging and the breasts, abdomen and pelvis should be shielded where possible. Ultrasound and MRI can be considered alternatives as they have no adverse fetal effects, though the latter is not routinely used in the acute trauma setting due to extended image acquisition times, especially in the critically unwell patient.
CTG remains the primary investigation for assessment of fetal wellbeing and uterine activity in women after 24 weeks gestation. Fetal heart rate abnormalities, which occur as a result of compromised fetal perfusion and oxygenation, may be predictive of placental abruption, fetal hypoxic injury and potentially fetal demise, but sensitivity remains at only 62 per cent. However, when combined with a normal physical examination, the negative predictive value is 100 per cent in excluding adverse fetal outcomes.5
CTG should be applied as early as possible following primary survey and without delay after maternal stabilisation. The ideal duration of CTG monitoring remains unclear, with current trauma guidelines suggesting between four and 24 hours of observation and monitoring. Several small prospective studies have indicated that in the absence of uterine activity, vaginal loss or abnormalities of the fetal heart pattern, the CTG can be discontinued after four hours without any further adverse obstetric/fetal outcomes over an uninjured patient control group.6,7
The Kleihauer-Betke (KB) test is a blood test often used as a routine investigation to identify a fetal-maternal haemorrhage (FMH) that can occur in 10–30 per cent of pregnant women following trauma.8
However, the incidence of a positive KB test following maternal trauma has been shown to be no different to the incidence in low-risk pregnant women without a trauma history.9 This indicates that a positive KB test alone is insufficient to indicate a pathological FMH and the need for delivery. A significant FMH following trauma is usually diagnosed clinically on the basis of CTG changes, antepartum haemorrhage or intrauterine fetal demise, and does not require waiting for a blood test result to indicate need for delivery. The KB test can be useful in calculating the required dose of prophylactic Rh immunoglobulin and is required in Rhesus-negative women following trauma to prevent isoimmunisation from a small nonpathological bleed.
Ultrasound scan (USS) is a valuable tool in assessing pregnant women following trauma to ascertain accurate gestational age, fetal presentation, placental location, estimated fetal size, fetal wellbeing (including evidence of fetal anaemia through middle cerebral artery Dopplers) as well as potential injuries to mother and baby. USS is not a sensitive investigation in the diagnosis of placental abruption, with 50–80 per cent of abruptions missed on scan alone.10 11 Furthermore, there is currently no evidence to support the use of biophysical profiles to predict adverse obstetric outcomes and need for delivery in the trauma setting.
Trauma in pregnancy requires a multidisciplinary approach, combining the experience of the emergency physicians, trauma surgeons, radiologists, obstetricians and paediatricians, to improve both maternal and fetal outcomes. Maternal resuscitation and investigation of maternal injury remains the primary focus initially, switching to assessment of fetal wellbeing once the mother is stabilised. Clinical examination and fetal heart rate monitoring are the most predictive features in identifying adverse fetal outcomes, with further investigations, including the KB test and ultrasound, providing an adjunctive role.