Hemoglobin, hematocrit. Dilutional physiologic anemia may lead to hemato­crit in low 30% range by the 30th week.

WBC. Increased. During labor and the puerperium, normal white blood cell count may reach 20,000 or higher. Evaluate for other causes of elevated WBC. Elevation may be seen secondary to the stress of trauma.

Coagulation. Pregnancy is a hypercoagulable state that leads to increased risk of clot formation or DIC with ­certain kinds of trauma. Abdominal trauma may cause placental abruption or intrauterine death, leading to DIC. Average fibrinogen level in pregnancy is 450 mg/dL.

Respiratory. Functional residual volume is decreased. The apneic pregnant woman develops hypoxia more rapidly. PCO₂ is decreased to 30 with a compensatory drop in maternal serum CO₂ to allow a gradient for diffusion of fetal CO₂.

Gastrointestinal. Abdominal wall may be less sensitive to peritoneal irritation because of stretching of abdominal muscles from uterine growth. Significant intra-abdominal injury may be present without significant symptoms or signs. General intestinal relaxation with slow gastric emptying may lead to an increased risk of aspiration.

Genitourinary. There is an increased risk of bladder injury because of the bladder rising out of the pelvis.

Diagnostic Tests

Lab Tests. Basic trauma lab includes type and crossmatch, Rh status, and antibody test. Regardless of Rh status, a positive Kleihauer-Betke (K-B) test may predict the risk of preterm labor. With a negative test, post-trauma electronic fetal monitoring may be limited to a shorter period. With a positive test, significant risk of preterm labor may require longer monitoring; therefore, K-B testing has important advantages to all maternal trauma victims.³ However, a positive test does not necessarily indicate pathologic fetal-maternal hemorrhage.⁴

If placental trauma or abruption is suspected, add coagulation profile (fibrinogen and fibrin degradation products) with INR-PTT.

Ultrasound. FAST scan is a safe, rapid method to identify intra-abdominal free fluid.⁵ In addition, it can assess fetal viability and condition.

Peritoneal Lavage⁶. Rarely done, generally based on surgeon’s discretion or lack of imaging options.

Imaging – Plain & CT.⁷ Generally, a complete trauma exam with CT scanning will not approach levels that adversely affect the fetus. If possible, fetal exposure to radiation should be minimized by shielding abdomen/pelvis with a lead apron. Consider another study (e.g., ultrasound) if it will provide comparable information.

However, diagnostic techniques to evaluate potentially serious traumatic injury to the mother should not be withheld for fetal concerns.