Trauma and Related Surgery in Pregnancy

Fetal Physiology

Several factors are important in determining the impact of a traumatic event on pregnancy outcome. These include gestational age, type and severity of trauma, and the extent of disruption of normal maternal and fetal physiology.

In the first week following conception, the nonimplanted embryo is relatively resistant to noxious stimuli. During the first trimester, the uterus resides relatively safely within the confines of the bony pelvis and has reached just above the pubic symphysis by 13 to 14 weeks’ gestation. As such, the uterus is protected to a large degree from direct trauma. However, maternal hypovolemia may have a significant impact on the developing embryo/fetus at any gestational age. Pregnancy loss in the first trimester is not likely related to direct uterine injury but more so from physiologic cardiovascular changes that occur during maternal hypovolemia and associated hypotension, resulting in hypoperfusion of the uterus and the developing fetus. Uterine blood flow is not autoregulated and is maximally dilated in the normal physiologic state. Maternal hypovolemia may result in vasoconstriction in vascular beds, including the uterine vessels. In experimental hypovolemic shock, pregnant sheep will decrease uterine blood flow at rates greater than would be expected with a decrease in maternal blood pressure alone. Even in the absence of uterine artery vasoconstriction, decreases in maternal blood pressure as a result of hypovolemia will result in decreased uterine blood flow. These phenomena underlie the importance of maintaining adequate maternal blood volume as an initial step in fetal resuscitation. The third-trimester fetus can adapt to decreased uterine blood flow and oxygen delivery by redistributing blood flow to the heart, brain, and adrenal glands. Furthermore, because fetal hemoglobin has a greater affinity for oxygen than adult hemoglobin, fetal oxygen consumption does not decrease until oxygen delivery is reduced by 50%.

The leading cause of blunt abdominal trauma in pregnancy is motor vehicle accidents . Penetrating trauma is typically the result of gunshot and stab injuries. Both blunt and penetrating trauma may result in the rupture of the amniotic membranes. In the mid second trimester, membrane rupture with oligohydramnios may result in pulmonary hypoplasia or orthopedic deformity. Injury to the placenta may precipitate placental abruption and lead to fetal anemia, hypovolemia and hypoxemia. Maternal mortality risk with penetrating trauma is more favorable than with blunt trauma because nonreproductive viscera are provided some protection by the gravid uterus, which absorbs the projectile objects.

Maternal Anatomic and Physiologic Changes

Nearly every maternal organ system undergoes anatomic or physiologic changes during pregnancy. The description that follows emphasizes consideration of these changes that affect trauma management.

A major concern in the management of trauma victims is the potential for internal hemorrhage and hypovolemia. The sentinel findings on examination are vital sign abnormalities, typically hypotension and tachycardia. Consideration should be given to the normal decrease in systemic vascular resistance that results in a decrease in mean blood pressure of 10 to 15 mm Hg and an increase in pulse of 5 to 15 beats/min, particularly in the second trimester. These changes can be accentuated if the trauma victim is placed in the supine position (e.g., strapped to a long board to secure the cervical spine). The resultant potential decrease in venous return from the lower extremities can reduce central venous volume and result in a diminished cardiac output by as much as 30%. Simple manual displacement of the uterus to the left or placement of a rolled towel under the backboard while ensuring that the spine remains secure alleviates most of this effect.

Blood volume increases by a mean of 50% in the singleton gestation. This is usually maximized by 28 to 30 weeks’ gestation. Red blood cell mass increases to a lesser degree than does plasma volume, resulting in a slight decrease in hemoglobin concentration and a decrease in hematocrit. Iron-deficiency anemia is also common during pregnancy, and together with the normal dilution, hemoglobin concentrations may often be as low as 9 to 11 g/dL. These hematologic changes have two potential implications: anemia may be confused with active bleeding and hypovolemia, and blood volume estimates should be adjusted upward during fluid resuscitation.

Several major pregnancy-induced changes in the gastrointestinal tract are also important for trauma management. Compartmentalization of the bowel upward serves to protect it during lower abdominal trauma but increases the risk of injury when penetrating trauma to the upper abdomen occurs late in pregnancy. Complex injuries to the small intestine can be encountered with multiple entry and exit wounds as a result of its being crowded and compacted into the upper abdomen. Decreased gastric motility results in a prolonged gastric emptying times, thereby increasing the risk of aspiration associated with general anesthesia. Rebound tenderness and guarding may be less apparent in later gestation, because of stretching and attenuation of the abdominal musculature and peritoneum.

The dramatic increase in uterine blood flow, up to 600 mL/min, may result in rapid exsanguination in the event of an avulsion or injury to the uterine vasculature or rupture of the uterus. Retroperitoneal hemorrhage from remarkably dilated pelvic vasculature is a common complication of pelvic fracture.

Motor Vehicle Crashes

A number of human factors are related to traffic-related injuries and fatalities in the United States. For many reasons, drivers have increasingly become more distracted while driving. Cell phone use and texting while driving are contributing factors. Consequently, states laws banning cell phone use and texting have increased over the last decade.

According to the National Highway Transportation Safety Administration (NHTSA) report for 2012, a MVC occurs every 14 seconds, an injury every 14 seconds, and a death, on average, every 16 minutes in the United States. MVCs are the most common cause of trauma-associated fetal loss in the United States . The likelihood that an MVC will result in fetal loss is directly related to crash severity and to the severity of the maternal injury. For example, estimates based on case series would suggest that only about 1% of minor MVCs will result in abruptio placentae, whereas clinically evident abruption occurs in as many as 40% to 50% of severe blunt maternal trauma cases. In addition, the lack of seatbelt use has been found to be associated with fetal loss, particularly if the mother has experienced ejection from the vehicle and head trauma. However, even a seemingly minor MVC, without substantial maternal injury, may result in placental abruption and fetal loss because of exposure to the shearing acceleration-deceleration forces previously described.

Internationally, road injuries contribute significantly to morbidity and mortality in developing countries. While specific maternal injury rates are difficulty to determine, road injuries killed 231,000 people in sub-Saharan Africa in 2010, accounting for almost one-fifth of the global road injury death toll.

Falls

Because pregnancy changes the center of gravity and results in postural instability, loss of balance is not uncommon, and the likelihood of a significant fall is increased. A retrospective study found that as many as a quarter of pregnant women experience a fall at some time during pregnancy. Like MVCs, falls expose the placenta to the shearing forces associated with blunt trauma. However, compared with MVCs, the likelihood that a fall may result in placental abruption and fetal death is low, accounting for only 3% of trauma-associated fetal deaths in one study . In a more recent prospective cohort study that involved 153 women who experienced falls during pregnancy, no instances of placental abruption were reported. Nonetheless, compared with pregnant women who did not experience a fall-related hospitalization during pregnancy, women hospitalized for falls remain at an increased risk for adverse outcomes in their pregnancy. One retrospective cohort study of 693 women hospitalized for falls during pregnancy, most of whom were in the third trimester, found that these women were at an increased risk for preterm labor, placental abruption, cesarean delivery, “fetal distress,” and fetal hypoxia.

Domestic Violence and Intimate Partner Violence

Pregnant women are at increased risk to suffer violent assault compared with nonpregnant women. The period prevalence of IPV during pregnancy has been reported to range from 6% to 22%; up to 45% of pregnant women report a history of domestic abuse at some time during their lifetime. The rates of suicide and homicide in pregnancy have been reported as approximately 2.0 per 100,000 and 2.9 per 100,000 live births, respectively. African-American women account for 17.7% of live births but nearly half (44.6%) of pregnancy-related homicides, and of these, 45.3% were associated with IPV. Victims of suicide were more likely to be older and white, and 54.3% of pregnancy-associated suicides involved IPV. The National Violent Death Reporting System reported that there were 94 pregnancy-associated suicides and 139 pregnancy-associated homicides in the United States from 2003 to 2007, yielding maternal death rates of 2.0 and 2.9 deaths per 100,000 live births. A Colorado population study reported that 30% of maternal deaths between 2004 and 2012 were a result of self-harm. The pregnancy-related death ratio was 5.0% for overdose and 4.6% for suicide (both per 100,000 live births). Deaths were evenly distributed throughout the first postpartum year, with only six maternal deaths occurring during pregnancy itself. Similarly, a study from Ontario, Canada reported that the maternal suicide rate was 2.58 per 100,000 live births, with suicide accounting for 51 (5.3%) of 966 maternal deaths.

Common methods of self-inflicted attempted suicide are drug overdose and poisoning with a corrosive substance. In one study, murder was the most frequent cause of death during pregnancy and in the subsequent year, and the majority of the perpetrators were found to be current or former intimate partners. This analysis of pregnancy-associated homicides found that intimate partner homicides were most likely to occur during the first 3 months of pregnancy. In a United States-based study, 5% of female homicide victims were pregnant. Although DV occurs in all ethnic and socioeconomic groups, African American and Native American women as well as women from households with lower incomes are at increased risk. Intentional trauma during pregnancy has a 2.7-fold risk (95% confidence interval [CI], 1.3 to 5.7) for preterm birth and a 5.3-fold risk (95% CI, 3.99 to 7.3) for low birthweight. According to a California database study of maternal discharge records between 1991 and 1999, assaults were significantly associated with uterine rupture and conferred significant risks for placental abruption and low birthweight, even if the victim was not delivered during the initial hospitalization.

Fractures

Fractures are the most common type of maternal injury to require hospitalization during pregnancy, while the lower extremities are the most common site of fractures that complicate pregnancy. Although pelvic fractures are less frequent than fractures of the extremities, pelvic fractures are most likely to result in adverse outcomes, including placental abruption and perinatal and infant mortality ( Fig. 32.1 ). Leggon and colleagues reported on a total of 101 pelvic or acetabular fractures in pregnant women, and the three most common reasons for injury were MVC (73%), falls (14%), and pedestrian struck by an automobile (13%). The overall fetal mortality rate in pelvic and acetabular fractures was 35% compared with 9% maternal mortality. Thus, pelvic fractures are thought to be an independent risk factor for adverse fetal outcome. Pelvic fractures may also be associated with significant maternal hemorrhage and shock as a result of significant hypertrophy of the pelvic retroperitoneal vasculature and subsequent laceration of these vessels because of sharp bone fragments. Pelvic fractures may also be associated with bladder and urethral trauma. Pelvic fractures are not a contraindication to vaginal delivery, unless the fracture results in obstruction of the birth canal or if the pelvic fracture is unstable; more than 80% of women who have sustained pelvic fractures can deliver vaginally.

Penetrating Trauma

Gunshot and stab wounds are the most frequent types of penetrating trauma encountered during pregnancy. Penetrating trauma in a pregnant woman are less likely to result in death than in a nonpregnant individual, owing to the protective effect of the gravid uterus when penetrating wounds occur in the upper abdomen. However, penetrating trauma poses major risk for complex maternal bowel injury because of the compartmentalization of the bowel in the upper abdomen by the enlarged uterus. Gunshot wounds to the abdomen require exploratory surgery to determine the degree of abdominal viscera injury and debridement of damaged tissues. A stab wound in a pregnant woman should be managed the same as in a nonpregnant woman. Bowel injury with spillage of the intestinal contents increases the risk for peritonitis and pregnancy loss from infection. Penetrating trauma to the uterus is strongly associated with poor fetal outcome. Fetal death is dependent upon the degree of placental or umbilical cord disruption. The risk of fetal death has been reported to be as high as 71% after gunshot wounds and as high as 42% following stabbings.