Trauma occurs in up to 6-7% of pregnancies¹. Mechanisms of injury in pregnant trauma patients leading to presentation at a health service vary considerably, but most commonly are the result of motor vehicle accidents, falls and domestic or intimate partner violence.² A high suspicion for injury in a pregnant patient, even in minor trauma, is important. The risk of significant injury increases with the severity of trauma and stage of pregnancy.
Every female patient of child-bearing age should be asked if they are or could be pregnant, and all females of child-bearing age should have a pregnancy test as part of their secondary survey unless they are already known to be pregnant.³
Obstetric trauma patients present special challenges for the response team on arrival at a healthcare facility. The need for coordinated and synchronous assessment of both the mother and fetus  with the potential need for urgent interventions for both may create significant stress for staff and for the health service.
Additionally, the many physiological changes of pregnancy predispose pregnant trauma patients to further risks and introduce new challenges, with modifications in positioning, resuscitative efforts and transfer arrangements required. Although management requires urgent assessment and treatment of both the mother and unborn child, it is important to emphasise that a clear focus on resuscitative measures to stabilise the mother is crucial to optimising the outcome for both.

Pregnancy causes physiological change in many body systems. As a result, normal models of trauma care must be modified for pregnant trauma patients. The adaptations of pregnancy that are important in trauma care include the following.⁵ 

Cardiovascular
Blood pressure	Minimal change Slight ↓ in first and second trimester, normal in third
Heart rate	↑ 15–20% ↑
Cardiac output	↑ 30–40% 6–7 L/min during pregnancy
ECG	Non-specific ST changes, Q waves in leads III and AVF, atrial and ventricular ectopics
Systemic vascular resistance	↓ to 1,000–14,000 Due to progesterone and blood volume
Respiratory
Respiratory rate	No change
Oxygen demand	↑ 15%
Functional residual capacity	↓ 25%
Minute ventilation	↑ 25–50% or 7–15 mL/min
Tidal volume	↑ 25–40% or 8–10 mL/kg
PaO2	↑ 10 mmHg or 104–108 mmHg
PaCO2	↓ 27–32 mmHg
Arterial pH	↑ 7.40–7.45
Bicarbonate	↓ 19–25 mmol/l
Haematological
Blood volume (mL)	↑ 30–50% volume
White cell count (mm3)	↑ to 5,000–14,000
Haemoglobin (g/dL)	↓ to 100–140
Haemocrit (%)	32–42
Plasma volume (mL)	↑ 30–50%
Red blood count volume (mL)	↑ to 1,900
Coagulation factors ↑ 30–50%	↑ factors VII, VIII, IX, XII
Platelet (mm3)	200,000–350,000
Fibrinogen, plasma (mg/dL)	264–615
Renal
Urea (mg/dL)	4–12
Sodium (mEg/L)	132–140
Potassium (mEg/L)	3.5–4.5
Chloride (mEg/L)	90–105
Calcium ionised (mEg/L)	4–5

Changes in resting heart rate, blood pressure and cardiac output may mask signs of hypovolemia, and pregnant women can experience blood loss of up to 30% of their circulating volume without significant changes or visible clinical signs. The first sign of maternal shock may be fetal distress.

It is important to note that all pregnant women greater than 20 weeks gestation should be managed in a left lateral tilt position (15–30 degrees) to reduce the impact of aortocaval compression by the enlarged uterus. Alternatively/additionally, the uterus may be manually displaced.

 

Pregnant women have reduced respiratory function and oxygen reserve as a result of:

They are predisposed to rapid changes in oxygen saturation and so intubation and ventilation are often more difficult than in a non-pregnant trauma patient.

Glomerular filtration rate and renal blood flow increase during pregnancy, sometimes with a decrease in serum creatinine and urea. Glycosuria is a common finding on urinalysis.  Haematuria is not normal in pregnancy and should be considered a significant finding in the trauma setting.
 

Trauma, whether minor or major, can have significant negative health effects on a mother and baby. It is estimated that 1-3% of minor trauma to a pregnant mother results in loss of the fetus, and there should be greater concern with increasing severity. ^{6 7}

Pregnancy specific complications to be considered in trauma include the following: