|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 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|
|Blood volume (mL)||↑ 30–50% volume|
|White cell count (mm3)||↑ to 5,000–14,000|
|Haemoglobin (g/dL)||↓ to 100–140|
|Plasma volume (mL)||↑ 30–50%|
|Red blood count volume (mL)||↑ to 1,900|
|Coagulation factors ↑ 30–50%||↑ factors VII, VIII, IX, XII|
|Fibrinogen, plasma (mg/dL)||264–615|
|Calcium ionised (mEg/L)||4–5|
Used with permission from: The Royal Melbourne Hospital. Trauma Service. Emergency and Trauma Services. Pregnancy and trauma guideline. Melbourne: Advisory Committee on Trauma. 2009 Nov.
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.
Used with permission from Sally Pairman, Jan Pincombe, Carol Thorogood and Sally Tracy;
Midwifery: Preparation for Practice © 2006 Sydney, Elsevier Australia.
Until the end of the first trimester, the uterus is relatively protected by its position within the pelvic structures and its thick-walled anatomy. By full term, the uterus has reached its maximum height (at the costal margins), is exposed within the abdominal cavity, is thin-walled and contains a large volume of blood. The blood flow to the uterus at term is 800–1,000 mL/min. Therefore there is significant risk for massive blood loss from an injury to the uterus or pelvic structures.
Pregnant patients are susceptible to aspiration due to slowed gastric emptying and increased acidity of the gastric contents. A full stomach should be assumed during management of any pregnant trauma patient. A nasogastric tube (NGT) or orogastric tube (OGT) should be inserted for patients who are intubated.
White cell count, clotting factor amount and plasma proteins are increased in pregnant patients, increasing the risk of thromboembolism. Low or borderline platelet levels (100–150 × 109/L) are common in pregnancy. Measured reference ranges of clotting remain the same in pregnancy.