10-19: Third-Trimester Blunt Abdominal Trauma

Clinical Summary

Trauma is a major cause of maternal and fetal mortality. In addition to injuries to abdominal organs seen in nonpregnant patients, preterm labor, fetal-maternal hemorrhage, uterine rupture, and, most importantly, abruptio placentae may result from blunt trauma during pregnancy. Abruptio placentae, the premature separation of the placenta from the site of uterine implantation, is found in up to 50% of major blunt trauma patients and up to 5% of those with apparent minor injuries. Signs of uterine hyperactivity and fetal distress are commonly seen when significant placental detachment occurs. Most patients have vaginal bleeding, but up to 20% will present with little or no external bleeding when the margins of detachment are above the cervical os.

Electronic fetal monitoring for a minimum of 4 hours is indicated in all cases of significant trauma in patients beyond 20 weeks’ gestation. Normal fetal heart rates average between 120 and 160 bpm. Rapid, frequent fluctuations in the baseline are characteristic of normal “reactivity.” The loss of this reactivity can occur during a normal fetal sleep cycle, following narcotic administration, or in the setting of fetal hypoxia or distress. Significant transient decelerations in fetal heart rate are classified as early, late, or variable depending on how they correlate with uterine contractions (via tocometry). Late and variable decelerations are concerning for fetal distress due to maternal hypotension and/or hypovolemia in trauma.

Management and Disposition

In addition to a standard trauma evaluation, immediate obstetrician consultation for all pregnant trauma patients beyond 20 weeks’ gestation is imperative. Obtain blood for type and cross-matching, CBC, prothrombin time (PT), partial thromboplastin time (PTT), fibrinogen, and fibrin degradation products or D-dimer. Continuous tocometric fetal heart rate monitoring is required for a minimum of 4 hours to rule out preterm labor or fetal distress. US is essential in visualizing placental abruption and differentiates this from vaginal bleeding due to placenta previa or other causes. Indications for emergency cesarean section include placental abruption, signs of ongoing fetal distress, or uncontrolled maternal hemorrhage.

Pearls

1. Ecchymosis from blunt force may not develop on a gravid abdomen. A careful history of the mechanism of trauma and complaints is essential.

2. Anti-Rh immunoglobulin should be administered for all Rh-negative mothers with significant third-trimester blunt abdominal trauma.

3. Laboratory evidence of a consumptive coagulopathy may be seen with significant abruption.

4. Placental abruption, or abruptio placentae, can also occur spontaneously and should be considered in any pregnant patient at greater than 20 weeks’ gestation with severe abdominal pain (with or without vaginal bleeding), uterine irritability, and/or fetal distress.