Be Prepared to Manage Severely Injured Pregnant Women

Standard lab values must be seen in the context of the changes in maternal physiology. For example, blood gas values in pregnancy may reveal lower CO2 values, and hematocrits may be lower secondary to the hemodilution seen in blood volume expansion.

During evaluation or resuscitation, it is important for ob.gyns. to remind the team of the mass of the gravid uterus and its ability—when the woman is in the supine position—to compromise the return of blood flow to the heart by compressing the vena cava.

Beyond the second trimester, the patient should be tilted to the left by approximately 35 degrees, and when a full-body tilt is not possible, left lateral displacement of the uterus must be maintained. When spinal injury is suspected, care must be taken to keep the spine and neck aligned during tilting.

Questions About Imaging

The obstetrician often will be asked whether the imaging needed to diagnose various injuries is safe for the fetus. Doses of radiation used during trauma care and evaluation—for example, CT scans of the pelvis or chest, and chest x-rays—are usually in the range of less than 250 mGy, which is considered to be the intermediate range of exposure and reasonably safe for the fetus.

Whenever possible, the pelvis of a pregnant woman should be shielded, especially in the first trimester. It is important to know, however, that much of today's imaging equipment is faster than previous technology and therefore delivers much lower radiation exposure with more information in a single pass. Additionally, MRI has been shown to be a safe modality in pregnancy.

The bottom line is that imaging studies that are needed for the care of the critically injured patient should not be withheld because she may be pregnant.

Primary Assessment

On initial presentation, all efforts for the pregnant trauma patient must first be directed toward stabilizing the mother and maintaining oxygen delivery, with the ABCs (airway, breathing, and circulation) of trauma care being the first priority.

Women who are pregnant have a reduced ability to compensate for respiratory compromise. Maintaining a patent airway is critical for both maternal and fetal oxygenation, and this very well may require early intubation. We must make sure that the patient is moving oxygen in, with oxygen saturation levels better than 90%.

The fetus's oxygen uptake depends directly on oxygen delivery via uterine blood flow, so circulation—both to the mother's vital organs and to the uterus—is also key. Because of shunting and vasospasm, significant uterine blood flow compromise may exist even with normal-appearing blood pressure. Thus, it is important to control any significant bleeding and pursue vigorous volume replacement.

Only after the ABCs are addressed—and readdressed for effectiveness—can we turn our attention elsewhere. If we were to add a “D” to the trauma protocol, it would stand for “disability” and would involve a rapid neurologic evaluation to assess for any neurologic injury. It is worth considering that neurologic impairment in late pregnancy may be secondary to an eclamptic seizure that may have led to the trauma event.

Other often critical components of trauma injuries, such as fractures and intraperitoneal hemorrhage, are usually evaluated almost simultaneously by the trauma team.

Patients with pelvic fractures (common in motor vehicle accidents) are at risk of having retroperitoneal hemorrhage, which is not always obvious and requires careful diagnosis. A pelvic exam can reveal signs of lower pelvic fracture and possible vaginal lacerations from protruding bone fragments.

The Secondary Survey

Once we have stabilized the mother and evaluated her for other critical signs of trauma, we can turn our attention to fetal assessment. First, we should assess gestational age, either by taking a history if someone close to the mother is present, or through ultrasonography.

Ultrasonography is an important tool at this point for assessing several factors in short order. In addition to assessing the viability of the fetus, we can evaluate the intrauterine fluid volume and the placental location. (The question of viability, of course, depends on the level of neonatal intensive care services available).

A low amount of amniotic fluid should lead us to suspect rupture of the amniotic membranes or, in some cases, uterine rupture secondary to trauma. Although with expert hands it is possible to detect relatively small placental abruptions, abruptions are usually apparent only with larger separations.

Ultrasonography can also be used in determining intra-abdominal free fluid which is consistent with intraperitoneal hemorrhage.

When the woman is severely injured and needs surgery and if delivery of the fetus is unnecessary, we should focus on monitoring the fetus in the operating room. We can do so with an ultrasound probe or a fetal Doppler encased in a sterile sleeve.