Trauma in pregnancy
Trauma is a leading cause of mortality in pregnancy. Pregnancy increases the incidence and severity of abdominal trauma in females.
Trauma affects up to 7% of pregnancies and the incidence of pregnancy in level 1 trauma patients is estimated to be ~2% 1.
90-95% relates to blunt trauma and 5-10% relates to penetrating trauma 1,5. Causes include (from most to least prevalent in the United States):
- motor vehicle collisions
- assaults (including domestic violence)
- stab wounds
Traumatic injuries in pregnancy are divided into maternal injuries, injuries to the gravid uterus and injuries to the fetus.
Maternal death rates from traumatic injuries are the same as the death rate in non-pregnant patients.
Severe abdominal injury is more common in pregnant than non-pregnant patients. The range of injuries is similar but the following are more common in pregnant patients due to the physiological and anatomical changes of pregnancy 1:
- retroperitoneal haemorrhage
- bladder injury
- liver injury
- splenic injury
- renal injury
- retroperitoneal haemorrhage: risk increases due to increased pelvic blood flow
Pelvic and acetabular fractures are associated with a high fetal mortality.
In penetrating injury, the mother is actually protected by the enlarged uterus but consequently the uterus and fetus are more likely to be injured.
When the mother survives, the most common causes of fetal demise are placental abruption and maternal haemorrhage.
Injury to the gravid uterus
The majority of injuries to the gravid uterus occur in the third trimester. Injuries that can occur to the gravid uterus as a result of trauma includes:
- spontaneous abortion
- preterm labour
- premature rupture of membranes
- placental abruption
- placental laceration and/or infarction
- uterine laceration and/or rupture
Placental abruption is the most common injury in the uterus following blunt trauma. Uterine rupture and laceration are uncommon.
Placental abruption is classified according to the site: marginal (most common), retro-placental and pre-placental. On CT, findings suggestive of placental abruption are a heterogeneous placenta with areas of non-enhancement. Placental abruption is not a straight forward diagnosis and CT can result in both false-negatives and false-positives. It can be difficult to determine whether focal placental thickening is from retroplacental clot, is a normal placenta or myometrial contraction.
In the third trimester, it can be particularly difficult to determine whether the appearance of the placenta is sinister or not. Prominent chorionic villous plate indentations may resemble ischaemic changes and venous lake may resemble active bleeding in the placenta. CT is only used to diagnose placental abruption if the CT has been performed to exclude maternal injury.
If there is no concern about maternal injury then ultrasound is the investigation of choice. However, ultrasound is also insensitive for abruption and cannot exclude it. External fetal monitoring is used to dictate ongoing management.
Injury to the fetus
Direct injury to the fetus is uncommon as it is protected by the maternal body wall, the uterus and amniotic fluid 1. Thus injuries to the fetus are most common in the third trimester when the volume of amniotic fluid relative to the volume of the fetus is reduced. Fetal skull fracture and head injury are the most common injuries are often due to maternal pelvic fracture.
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