Key principle: Do not withhold indicated imaging — maternal health is critical to fetal health. Typical trauma CT (abdomen/pelvis) delivers ~25 mGy to the fetus, well below the 50 mGy safety threshold. Prompt diagnosis of maternal injury protects both mother and fetus. IV iodinated contrast is safe in pregnancy (FDA Category B). Gadolinium: avoid unless benefits clearly outweigh fetal risk (FDA Category C).

CT Fetal Radiation Doses

CT Examination	Fetal Dose Estimate (mGy)
Head CT	~0
Chest CT / CTPA	0.2
Abdominal CT	4
Low-dose stone protocol	10
Abdomen & pelvis CT	25
Abdomen & pelvis CT angiography	34

Safety threshold: 50 mGy. Doses <50 mGy: no proven fetal harm. Doses 200–250 mGy: potential neural tube defects. Intellectual disability risk highest at 8–15 weeks gestation.

Clinical Algorithm

Hemodynamically unstable + FAST positive → laparotomy without further imaging delay
Hemodynamically stable: FAST first → if positive for free fluid or signs of peritonitis → CECT abdomen/pelvis
If FAST negative but clinical concern remains → CECT if indicated
US useful for targeted fetal assessment and gestational age confirmation at any stage
Laparotomy vs. observation in stable patients may be guided by CT findings and gestational age (>24 weeks → fetal monitoring)

Placental Abruption

Most important obstetric injury: Occurs in 20–50% of pregnant patients experiencing major trauma. Second most common cause of fetal death after maternal shock. US sensitivity is low — 50–80% of traumatic abruptions are missed prospectively at initial US. External fetal monitoring is more sensitive than US for abruption detection and should always be performed for at least several hours after trauma (even seemingly minor trauma, as 1–5% of "minor" cases result in abruption).

CT and US Abruption Features

Feature	CT Findings	US Findings
Acute hematoma / abruption	Heterogeneous placenta; area(s) of hypoattenuation or nonenhancement; retroplacental hyperattenuating blood	Retroplacental collection (hyperechoic acutely, becomes hypoechoic / isoechoic as hemorrhage evolves)
Normal variants (false positives)	Cotyledons, venous lakes, chorionic plate indentations, age-related infarcts — may mimic hypoattenuation. Geographic hypoattenuation is NOT specific for abruption.	Prominent venous lakes may mimic retroplacental hematoma — correlate with CT
Complete abruption	Total absence of placental perfusion/enhancement; associated hemoperitoneum	Avascular placenta on Doppler; absent or abnormal fetal cardiac activity
Rupture of membranes	Large volume of fluid in vagina with low volume of residual amniotic fluid; heterogeneous placenta	Oligohydramnios / anhydramnios; fluid in vagina

Traumatic Abruptio Placenta Scale (TAPS) — CT Grading

Grades based on degree of placental enhancement on CECT. Intended for 2nd and 3rd trimester. Clinical diagnosis of abruption must be present for grading to apply.

Grade	Placental Enhancement	Clinical Management
0	100% — homogeneous normal enhancement	Normal; expectant management; good clinical outcomes expected
1	>50% — small geographic hypoattenuation (likely normal variants: cotyledons, venous lakes, age-related infarcts)	Normal; expectant management; good clinical outcomes expected
2a	>50% — nongeographic hypoattenuation, full thickness, acute angles with myometrium	Increased probability of abruption; extended clinical monitoring recommended
2b	25–50% — larger area of decreased enhancement	Increased probability of abruption; extended clinical monitoring recommended
3	<25% — near-complete devascularization	Fetal death occurs frequently; consider immediate cesarean delivery if abruption confirmed

Uterine Rupture

Feature	Details
Incidence & significance	~0.6% of trauma in pregnancy; fetal mortality approaches 100%; maternal mortality ~10%
CT findings	Myometrial wall defect (most commonly fundus or anterior uterine wall); fetal parts external to uterine contour; hemoperitoneum; complex fluid adjacent to perforation site; diffusely heterogeneous uterus
US findings	Uterine contour defect; fetal parts outside uterus; intraperitoneal fluid; may be used intraoperatively
Risk factors	Prior cesarean delivery; prior uterine surgery; congenital anomalies; scarring. Blunt and penetrating mechanisms both implicated.

Fetal Injuries

Injury	Details
Direct fetal injury	Rare (<1% of trauma cases). Fetus relatively protected in 1st trimester by pelvic bones. Risk increases with gestational age.
Fetal skull fractures	CT more sensitive than US for bone detail. Fetal death in up to 35% when pelvic fracture present. Linear nondisplaced — monitoring without surgical intervention. Depressed fractures — percutaneous or surgical elevation.
Fetal intracranial hemorrhage	Identifiable on CT; associated with skull fractures; deceleration mechanism.
Rib / long bone fractures	May be seen on CT with severe pelvic trauma or direct compression.
Penetrating trauma	Severe fetal injury in 60–70% of penetrating trauma; fetal mortality 71–73% with gunshot wounds to the gravid uterus.

Nonobstetric Maternal Injuries — Pregnancy-Specific Considerations

Structure	Pregnancy-Specific Risk
Spleen	Displaced superiorly by gravid uterus; splenomegaly from increased blood volume → increased susceptibility to rupture
Liver	Displaced superiorly and compressed against rib cage; higher risk of laceration
Bowel	Displaced peripherally by uterus; increased risk of injury with penetrating trauma
Bladder	Elevated out of pelvis by gravid uterus; extraperitoneal rupture common. CT cystography or delayed CT imaging recommended if pelvic fracture + hematuria or clinical suspicion.
Pelvic fractures	Maternal mortality up to 9%. Fetal death in up to 35% when pelvic fracture present.
Vascular	Increased pelvic blood flow → higher risk of severe hemorrhage after blunt or penetrating pelvic trauma

Reporting Checklist

Placenta: estimate percentage of normal enhancement (TAPS grade if 2nd/3rd trimester); retroplacental or marginal hematoma; size of hypoattenuating area
Myometrium: wall contour intact or defect present; fetal parts within or outside uterine contour
Amniotic fluid: volume (oligohydramnios / anhydramnios); fluid in vagina (premature rupture of membranes)
Fetal: position (cephalic / breech / transverse); estimated gestational age; skull fractures; intracranial hemorrhage; long bone or rib fractures
Free fluid: intraperitoneal location and density (HU consistent with blood); hemoperitoneum volume estimate
Solid organs: liver, spleen, kidneys — AAST injury grade; active hemorrhage (contrast blush)
Pelvic ring: fracture type; acetabular involvement; proximity to fetal head
Bladder: wall integrity; extravasation on delayed images; cystography findings if performed

References

Langdon JH, Chai N, Patel A, et al. Imaging of Trauma in Pregnant Patients. RadioGraphics. 2025;45(10):e240043.

Trauma in Pregnancy — Imaging Safety, Placental Abruption, and CT Reporting