Management of the pregnant trauma patient: A literature study

AFE: Amniotic Fluid Embolism; CPR: Cardiopulmonary Resuscitation; CTG: Cardiotocography; DIC: Diffuse Intravascular Coagulation; DPL: Diagnostic Peritoneal Lavage; FAST: Focused Assessment with Sonography for Trauma; FHR: Fetal Heart Rate; FMH: Fetomaternal Haemorrhage; GA: Gestational Age; IM: Intramuscular; ISS: Injury Severity Score; KB test: Kleihauer-Betke test; LMWH: Low Molecular Weight Heparines; NPV: Negative Predictive Value; MVA: Motor Vehicle Accident; PA: Placental Abruption; PCS: Perimortem Caesarean Section; ROM: Rupture of Membranes; UR: Uterine Rupture

ISS is a valuable predictor of maternal outcome but it does not seem to accurately predict fetal outcome. Although having a high specifi city, several studies postulate that even a low ISS can be associated with adverse fetal outcomes [2,13,14,17,18].
There are several reasons why the management of the pregnant trauma patient is considered diffi cult: anatomical and physiological changes; diffi cult identifi cation of pregnancy specifi c complications; different mechanisms leading to potential injuries; rarity of presentation; hard risk stratifi cation; diffi cult prediction of outcome and fear of radiation exposure. Furthermore, it concerns two patients resulting in a cognitive burden and an incorrect diversion of attention towards the fetus. The need for a multidisciplinary approach further jeopardizes an uncomplicated management [4][5][6][7]9,10,17,18].
We provide an overview of the most important changes in pregnancy and their consequences as well as some important complications following trauma.
Different databases were searched including Pubmed, Cochrane, Medline and Embase. MeSH terms used were pregnancy, multiple trauma, wounds and injuries, and emergency treatment. Other terms used were polytrauma pregnant patient, trauma in pregnancy management, multiple trauma, pregnancy, trauma, management, perimortem caesarean section and perimortem caesarean delivery. A publication date fi lter was used including studies between 2008 and 2020. The obtained results were screened using title and/or abstract. The reference list of the selected articles was also browsed.
Exclusion criteria were: Not written in English, French or Dutch; no full-text available; case reports and series.

Results
A total of 30 articles were included in the qualitative synthesis ( Figure 1).

Anatomical and physiological changes
The management of a pregnant trauma patient is complicated due to anatomical and physiological changes of pregnancy [12]. Specifi cally, these changes can mask and mimic symptoms of injury but also predispose to trauma and alter the pattern of injury [10]. Therefore, understanding these modifi cations facilitates evaluation and management [2,4,10]. Table 1 gives an overview of the specifi c changes and their consequences.

Pregnancy associated complications
In case of suspected or confi rmed obstetrical complications, an urgent obstetric consultation is always warranted [6,17].
Fetal monitoring using cardiotocography (CTG) is the most available technique in detecting PA with a negative predictive value (NPV) of 100% [4,6,10,12,13,16,21]. Fetal distress is predictive of PA in 60% of all cases [19]. Fetal tracing may be reassuring until 30% of the placenta is separated from the uterus, whereas an uteroplacental separation of more than 50% is consistently fatal for the fetus [6,15,19].
Excessive uterine activity with more than four contractions per hour may be indicative of PA. More than eight contractions per hour in the fi rst four hours is consistent with the diagnosis of PA [10,18,21]. Eighty percent occur within six hours of monitoring but may be delayed for up to 48 hours or even longer [1,2,5,6,13,15,20,21,27]. However, PA has not been reported when there is less than 1 contraction every 10 minutes over a four hour period [12,13,27].
The management depends on the gestational age (GA) as  [6]. In case of fetal compromise while the mother is stable and a GA is higher than 23-24 weeks, emergency caesarean section is recommended to prevent coagulopathy and its adverse consequences [6,18,19,26]. There is no consensus whether emergency caesarean section should be performed in case of maternal instability [6,26]. When PA seems mild, betamethasone administration may be considered.
Furthermore, correction of haematological abnormalities and ultrasound follow up for evaluation of amniotic fl uid and fetal growth are recommended. [18,20,26].

Premature uterine contractions
The most common obstetric complication following trauma is premature contractions, especially if accompanied

Rupture of membranes
Following trauma, rupture of membranes (ROM) is possible causing preterm labour, umbilical cord prolapse with compression of umbilical vessels, infection or, if occurring in the second trimester, pulmonary hypoplasia or orthopaedic deformities [6,9,13,19]. If ROM is suspected, an external pelvic examination can assess vaginal fl uid leakage and nitrazine paper can be used to distinguish amniotic fl uid from normal vaginal secretions [6,11,17]. A digital vaginal examination should be avoided in order to reduce infection risk [15,17,18].

Preterm labour
Preterm labour can follow PA, ROM or premature uterine contractions [6]. It is associated with a higher risk of preterm delivery and should therefore be evaluated in every pregnant trauma patient [10,17,19]. The risk of preterm delivery is two times higher in pregnant trauma patients [6]. In case of regular uterine contractions, a fi bronectin test or cervical length assessment should be conducted in order to determine the risk of preterm labour [6].

Uterine rupture
A rare but life-threatening complication following trauma is an Uterine Rupture (UR) [6,7,10,20,27] [6,14,17,27]. Therefore urgent exploratory surgery may be recommended following abdominal trauma to reveal the extent of damage to uterus and adjacent organs as well as to avoid haemorrhage [1,6,10,19]. If the uterus is severely damaged, hysterectomy is recommended to prevent further deterioration of the maternal condition [1,19].

Amniotic fl uid embolism
Amniotic Fluid Embolism (AFE) is a rare complication of trauma [18]. It may occur following severe trauma due to a sudden increase in amniotic fl uid pressure at impact and the presence of vascular wounds [14]. Its incidence and mortality rate varies but it is certainly associated with a high maternal mortality rate [9,18,19,22]. Signs may include respiratory distress with hypoxia, shock or severe hypotension, seizures, coma and cardiac arrest [15,18,22]. Up to 50% will develop DIC or other coagulation disorders [9,14,18,22]. A high index of suspicion is warranted [18]. Echocardiography may show right heart strain or failure and increased pulmonary artery pressure [22]. Management includes supportive care and cardiopulmonary bypass should be considered [15,22].

Non-pregnancy associated complications: Pelvic fracture
Pelvic fractures are one of the most common non-obstetric complications of blunt trauma sustained in pregnancy, possibly due to increased pelvic laxity [15]. Pelvic fracture is an independent risk factor for poor fetal outcome and together with PA, it is the most common cause of fetal death following MVA [5,10,14,15,19].
Diagnosis is based on physical examination supplemented by pelvic X ray. [10,27] A vaginal speculum examination should be performed when a pelvic fracture is suspected, in order to exclude bleeding, ROM, vaginal lacerations or bony fragments [1,11].
Management may resemble that of the nonpregnant patient [26]. Pelvic binders are recommended for open book pelvic fractures to control haemorrhage [17]. Angioembolisation is a useful minimally invasive procedure to control haemorrhage from pelvic vessels not involved in the uterine circulation, although containing a high radiation dose [5,15].

General management
Pregnancy should be suspected in every female trauma patient of childbearing age until proven otherwise [4,6,17].
Thus, urine and serum pregnancy tests should be conducted in this female age group [4,6,19].
The management resembles that of a non-pregnant trauma patient [10,12,14,15,17,22]. However, some important considerations should be made regarding primary and secondary survey, as well as the management of cardiac arrest.

Primary survey
In pregnant women, the ABCDEF algorithm should be followed where F stands for fetus [2,20]. This indicates that the fetus is enclosed in the primary survey but after the initial assessment and stabilisation of the mother [4,6,[8][9][10]19,26].
Care should be taken while performing a left lateral tilt, preferably with a secured spine [4,6,8,10]. The threshold for intubation is lower in pregnant patients [17]. Preoxygenation with bag valve mask ventilation increases the risk of aspiration and therefore preoxygenation should be achieved by other techniques [11,17]. The pCO 2 goal after intubation is 28-35 mmHg to prevent respiratory alkalosis and decrease of uteroplacental fl ow [17].
The threshold for volume resuscitation is also lower in pregnancy [19]. However, an exaggerated fl uid resuscitation can lead to pulmonary oedema, and thus balanced fl uid resuscitation is crucial [17]. Since vasopressors compromise uteroplacental perfusion, they should only be administered in case of hypotension that is fl uid unresponsive [4][5][6]10].
Administration of bicarbonate should be used with caution [6].
The sensitivity and specifi city of FAST is comparable with non-pregnant trauma patients, however, differentiation between intra-and extrauterine fl uid can be challenging [4,9]. Traumatic brain injury is a major cause of maternal morbidity and mortality [15]. Also intracranial haemorrhage due to gestational diabetes mellitus and pregnancy induced hypertension should be considered [9].

Secondary survey
The secondary survey further evaluates the fetal state and the presence of uterine injury [7,8,20]. An obstetric consult is needed, especially when the fetus is potentially viable, obstetrical complications are suspected, or delivery is being considered [6,14,17].
GA must be estimated to assess viability, to direct management and to estimate radiation effects of radiologic examinations [4,11,14,18]. Comorbidities and complications of the current or previous pregnancies and deliveries should be assessed since they can affect management [4,6,17,19]. Inquiries should be made about fetal movement and specifi c symptoms such as contractions, vaginal leakage of fl uid or blood, haematuria, or pain [4][5][6]12,17].
During physical examination, the entire body is inspected and palpated, including the screening for signs of physical abuse [1,11]. In order to assess complications, an abdominal and pelvic examination must be conducted [15] . In the absence of concerning signs and symptoms, an external pelvic examination may be suffi cient [17]. However, in case of any concern, a sterile speculum examination should be performed to detect bleeding and identify its aetiology; assess cervical dilation and effacement; detect a prolapsed cord, a bulging perineum, a haematoma, vaginal lacerations, bony fragments, or ROM; assess the fetal position; or to identify fetal parts [1,4,5,6,[9][10][11][12]15,17,18,22]. A rectal examination allows for the identifi cation of blood and haematomas [4,10]. An ultrasound should be performed before the speculum examination to detect a placenta previa [4,6,10,15,17,18]. In case of a placenta previa, a digital vaginal examination should be avoided [9,10,15,17,18].
An abdominal examination is essential in order to detect ecchymoses which can indicate visceral injury. Abnormal abdominal distention can be a sign of intra-abdominal bleeding or organ perforation. Abdominal tenderness and contractions should be assessed in addition to palpation of the uterus and assessment of the fundal height, which can help determine the GA or indicate an abruption when increased [4,6,10,13,15,17,19]. Unexplained hypovolemia and rib or pelvic fractures raise the suspicion for intra-abdominal trauma [9]. After 20 weeks GA, fetal heart sounds should be auscultated [10].
A biochemical examination is mostly performed in case of minor trauma, although it is not predictive for fetal outcome Citation: Argent [3,12,17]. In case of major trauma or when PA or internal bleeding is suspected or confi rmed, an additional coagulation profi le is warranted [1,2,4,6,9,13,17,26]. Since fi brinogen levels are increased during pregnancy, low to normal levels indicate consumptive coagulopathy, especially when combined with low platelets and high fi brin degradation products [4,6,10,20,22]. Severe coagulopathy may be indicative of PA, AFE, or major bleeding [14]. An arterial blood gas is also of importance since maternal pH infl uences fetal oxygen delivery [4,9,10]. Additionally, the KB test may be helpful after 20 weeks of gestation in rhesus negative mothers when detecting more than 30 millilitres (ml) of fetal blood thereby guiding rhesus immunoglobulin administration [1,2,6,9,11,17,26,19].
In case of major trauma with large volume FMH, the KB test in combination with other features such as abdominal trauma and third trimester pregnancy can be a predictive risk factor for preterm labour and other adverse outcomes [1,4,9,11,12,15,20,22]. In case of minor trauma however, extended evaluation with fi brinogen levels, KB test and coagulation profi les should not be performed as they are not predictive of adverse outcomes [3,9].
Fetal and maternal heart rate should be compared in order not to misidentify maternal tachycardia as the fetal pulse [11,13]. Additionally, a waveform interpretation is paramount with repetitive late decelerations and loss of variability with sinusoidal pattern indicating fetal asphyxia or anemia [4,7,9,10,13,15,17,26]. Contraction frequency and regularity are also monitored with CTG [4,10,17]. Uterine activity of more than four contractions per hour may be indicative of PA or preterm contractions [7,18,21]. Besides frequency, the intensity of contractions are predictive of complications [6]. There is no agreement concerning the duration of monitoring but at least four to six hours is recommended [1,[4][5][6][7]9,[11][12][13][14][15][16][17][18]21,26]. In the absence of abdominal pain or vaginal bleeding, combined with a reassuring fetal heart tracing, there is no risk when there is less than one contraction every 10 minutes over a four hour period. In that case, the patient may be discharged if laboratory evaluation is normal and maternal state is reassuring [1,2,[4][5][6][7]10,12,13,17,20,27]. An obstetrical ultrasound should be carried out prior to discharge [6]. The combination of fetal monitoring with ultrasound provides the highest sensitivity and specifi city [19]. Fetal ultrasound should be performed urgently when delivery is being considered and GA is undetermined [6].
Since the risk for pulmonary embolism is increased during pregnancy in combination with immobilisation following trauma, the threshold for prophylactic heparin or Low Molecular Weight Heparines (LMWH) is lower [4,9,10,15,20,26]. Tranexamic acid, although not studied, can be administered in case of signifi cant haemorrhage and is safe for the fetus [9,14,17,26]. Tocolytics to suppress preterm labour in patients with a viable fetus and cervical changes can be considered [8,17,19,20]. Different options exist including the Intramuscular (IM) administration of 12 mg of betamethasone, although this may mask signs of shock due to its betamimetic effects [1,17,21]. Tocolytics should not be administered in case of fetal distress, maternal haemodynamic instability or if labour is considered to have a pathogenic etiology [17,19]. If labour and cervical changes progress despite tocolytics, the possibility of PA must be considered [1].
In case of non-reassuring fetal heart tracings, maternal resuscitation is essential [17,18]. If there is further fetal deterioration, emergency caesarean section is recommended even if a PA is not clinically evident [1,8,10,17,18].
Diagnostic peritoneal lavage (DPL) has largely been replaced by FAST although when FAST is ambiguous, DPL can be performed [4,10,15,26]. Abdominal CT may also be an alternative as it is also able to identify retroperitoneal damage [6]. The haemodynamically unstable pregnant trauma patient with a positive FAST or with stabbing or gunshot wounds to the abdomen should undergo an exploratory laparotomy [4,9,10,17]. This also applies the presence of meconium or vernix in the urine which suggest vesico-uterine rupture [15].
Although there is no robust evidence, effectiveness of CPR could be increased by tilting the mother 15-30° or by manual displacement of the uterus, the latter being preferred [1,4,6,7,14,17,[19][20][21][23][24][25][26]29]. If magnesium was given as a tocolytic prior to the arrest, it should be stopped and calcium should be administered instead. The focus of resuscitation

Declarations
Ethics approval and consent to participate:

Authors' contributions
LD'A and MS designed the work. LD'A collected the data.
LD'A and MS analysed the data. SV and MS substantively revised the manuscript. All authors read and approved the fi nal manuscript.
should be towards identifying type and aetiology of arrest [4,10,17,29]. BEAUCHOPS (Table 2) is a helpful tool to assess possible causes of maternal cardiac arrest. Fetal anoxia mainly occurs after a traumatic hypovolemic maternal cardiac arrest, and is associated with a bad outcome [1,11,23].

Perimortem caesarean section (PCS)
PCS consists of a caesarean section in a patient who is in extremis or is undergoing CPR [9]. Besides fetal survival, it can lead to a return of spontaneous circulation of the mother, making it a part of maternal resuscitation efforts [4,10,14,29].
Indeed, the best chance of fetal survival is maternal survival and that the latter can be achieved through fetal delivery [11].
There is no consensus concerning the order in which PCS or thoracotomy should be performed.

Conclusions
Preventive education about the use of seatbelts and airbags together with screening for domestic abuse and depression are essential in the follow-up of pregnant patients [5,6,10].
In case of trauma, pregnant patients should always visit a physician since the degree of trauma is not predictive of the outcome [4,10]. There should be a communication concerning the benefi t/risk of radiologic examinations. If no admission is needed, return precautions should be communicated such as