Follow the traditional airway, breathing, circulation, disability, and exposure assessment for maternal injury, and simultaneously stabilize and resuscitate the mother. After completing the primary survey and performing resuscitative steps, proceed with secondary assessment.
Begin with bedside expanded focused assessment with sonography for trauma to identify intra-abdominal or thoracic injury, and identify fetal activity and fetal heart rate. Transvaginal US can be performed once the mother is stabilized to complete the fetal survey and identify placental location. The sensitivity and specificity of abdominal US for the detection of intraperitoneal fluid are similar in pregnant and nonpregnant patients.9
Carefully select imaging studies to minimize fetal exposure to the potential adverse effects of ionizing radiation. Do not withhold imaging needed for appropriate maternal trauma management. The greatest risk to fetal viability from ionizing radiation is within the first 2 weeks after conception, and the highest potential for malformation is during embryonic organogenesis from 2 to 8 weeks after conception. The risk of CNS teratogenesis is highest when exposure occurs between weeks 8 and 15 (see Table 99-9). A dose <5 rad is the threshold for human teratogenesis.9 Fetal exposure can be decreased by shielding the maternal abdomen and pelvis during many studies and by performing modified studies and using dose-reducing techniques, such as decreasing the number of imaging slices obtained.
Standard trauma plain radiographs, such as cervical spine, chest, and pelvis films, deliver <1 rad (10 mGy) each. Abdominopelvic CT and pelvic angiography result in the highest delivered doses of radiation. The amount is typically 2.5 to 3.5 rad (25 to 35 mGy), with some variation due to equipment quality, techniques used, and duration of study. If abdominal-pelvic CT scanning is necessary to evaluate maternal status, CT also detects placental abruption, with a reported sensitivity of 86% and specificity of 98% for abruption.10 Table 99-10 provides the estimated amounts of fetal radiation exposure for some common trauma imaging studies.11
Potential effects of contrast agents employed in CT scanning are not well studied, and their use requires individualization, because iodinated agents can potentially cause neonatal hypothyroidism.
Perform pelvic examination only after US to determine placental location and exclude placenta previa.6 Do not perform pelvic examination if placenta previa is identified. A sterile pelvic examination can identify injuries of the lower genital tract, vaginal bleeding, and rupture of amniotic membranes.
To assess for amniotic membrane rupture, test vaginal fluid with pH paper. Fluid in the vagina with a pH of 7 is suggestive of amniotic fluid, whereas fluid with a pH of 5 is consistent with vaginal secretions. A branchlike pattern, or "ferning," seen upon drying of vaginal fluid on a microscope slide, also suggests amniotic fluid.
Obtain a CBC, serum chemistries, blood type and Rh status, coagulation profiles with fibrin degradation products and fibrinogen to assess for disseminated intravascular coagulation, and additional laboratory studies as clinically indicated. An Apt test or Kleihauer-Betke test can be performed by the laboratory. The Apt test is a qualitative determination of the presence of fetal hemoglobin in maternal blood. The Kleihauer-Betke test applies acid elution to an aliquot of maternal blood, and then maternal and fetal red blood cells are counted under the microscope. An extrapolation is then made regarding the volume of fetomaternal hemorrhage.
Serial Kleihauer-Betke testing can assess ongoing fetomaternal transfusion. If there is doubt whether the woman is pregnant or not, confirm pregnancy at the bedside with qualitative urine testing or with point-of-care US.