Pregnancy influences many physiologic changes to accommodate fetal metabolism, which present a unique set of challenges in the event of a traumatic injury to a pregnant patient [1]. Traumatic injuries are a leading cause of maternal cardiac arrest (MCA), a complex event further complicated by the dual management of the mother and the fetus [2–4]. Cardiac arrest can quickly result in hypoxic brain injury, which occurs faster in a pregnant woman due to alterations in blood composition during pregnancy and increased oxygen demand [5–7]. However, due to the altered fetal hemoglobin configuration, fetuses are relatively resilient to maternal hypoxia [7].

The gravid uterus presents another challenge in managing MCA, because it may impede the provider’s ability to effectively provide chest compressions [6, 8]. Manually generated cardiac output (CO) from compressions is only about 30% of normal CO [8]. Also, after the 20th week of pregnancy, the gravid uterus causes aorto-caval compression and further impedes both venous return and manually generated CO to no more than 10% [6, 8]. Evacuating the uterus rapidly resolves these impediments, and leads to uterine involution, allowing for a large autotransfusion and immediate increase in CO, which has been shown to increase rates of survival following traumatic MCA [5–11].

Resuscitative hysterotomy (RH), previously termed perimortem cesarean section, is critical to caring for the MCA patient. RH is an emergency cesarean section performed on a patient in middle-to-late pregnancy experiencing cardiac arrest, intended to improve the chances of maternal return of spontaneous circulation (ROSC) by reducing the aorto-caval compression caused by the fetus [5–10]. An algorithm for treating MCA is available from the American Heart Association, which suggests that RH should be initiated within 4 min of resuscitative efforts where cardiopulmonary resuscitation (CPR) is initiated but ROSC is not achieved, to facilitate delivery within 5 min [5–8, 12, 13]. In the setting of traumatic MCA, a vertical abdominal incision is recommended for greater visualization, though successful procedures have been documented using a Pfannenstiel incision [5–7]. Some studies suggest that RH can be done to prevent impending cardiovascular collapse, as a peri-arrest intervention, which accounts for longer times between patient arrival and initiation of the RH procedure [7, 9].

While RH is primarily indicated to optimize maternal outcomes, reported maternal and fetal survival rates after RH vary between studies. This is due to a multitude of factors including but not limited to location of arrest (in- or out-of-hospital), time between arrest and RH initiation, and cause of arrest. Studies reported generally high fetal survival rates for neonates > 24 weeks gestation, highlighting the importance of this procedure to fetal outcomes [10]. In RH secondary to traumatic MCA, the available data suggest that it is indicated in accordance with the 4-to-5-min rule, or if maternal survival is impossible [14]. In a study examining four RH patients presenting with hemodynamic instability from traumatic injuries, maternal survival was 50% and fetal survival was reported to be 100% [9]. Conversely, in out-of-hospital MCA, maternal survival is less than half of the national cardiac arrest survival rate (4.5% compared to 9.1%, respectively), and neonatal survival is 10-fold that of their mothers (45%) [10]. Despite these results, similar systematic reviews report higher maternal survival rates, where 54.3% [13] and 54% [6] of MCA patients survived to discharge. Einav et al additionally reported a clear benefit of RH in 31.7% of MCA patients [13].

This heterogeneity of results demands more focused studies of the outcomes of MCA patients undergoing RH to provide clarity and allow for better insight into treatment decisions that will provide the best patient outcomes. Data on the incidence and maternal outcomes in the setting of trauma are lacking, with fetal outcomes oftentimes unavailable. This is a notable limitation in the context of interpreting overall outcomes. Therefore, we sought to determine the maternal outcomes following RH in pregnant females arriving to the emergency department (ED) with traumatic injuries and herein present a descriptive analysis of the latter.

We obtained data from the American College of Surgeons Trauma Quality Improvement Program (TQIP) database [4, 15, 16]. The US Army Institute of Surgical Research regulatory office reviewed protocol H-26-003nh and determined that it met the definition of research not involving human subjects. We obtained only de-identified data.

The TQIP database has been maintained by the American College of Surgeons since 2008. The database includes mandatory data collection for level 1 trauma centers and collects data from other centers that do not meet level 1 criteria. The goal of the program is to provide data to aid trauma centers in standardizing trauma care, providing local and national quality improvement, and to provide data needed for best practices guidelines. As of 2023, there are over 800 participating centers where trained registrars enter data for trauma visits that meet entry criteria. The 2023 dataset represents the most recently available dataset as of the time of this analysis.

We included cases for which the sex was documented as female and there was a relevant procedure code with a procedure start time that was less than or equal to the ED length of stay (Fig. 1). We assumed that all deliveries performed in the ED were unplanned and emergent. We used the International Classification of Diseases version 10 codes that included any procedure code that starts with the following: 10A, 10D, 10E, 10H, 10J, 10P, 10S, 10T, and 10Y. In addition to the documented procedure, there had to be documentation of a pregnancy diagnostic code and/or the pregnancy preexisting condition variable (available in TQIP 2020-2023; Fig. 1). Other procedures were identified using relevant procedure codes which have been previously described [17, 18]. Due to the use of de-identified data, we could not reliably match maternal data to neonatal data and could not assess neonatal outcomes in conjunction with their corresponding maternal outcomes. As such, we have compiled a description of maternal outcomes noting the limitation of missing neonatal outcomes. Future studies may seek to obtain matched cohorts of maternal and neonatal data for improved insight into how maternal and neonatal outcomes influence one another. Signs of life were defined as a heart rate, respiratory rate, or systolic pressure greater than 0 or a Glasgow coma scale of greater than 3.

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Figure 1. Flow diagram outlining cohort selection.

We performed all statistical analysis using Microsoft Excel (version 365, Redmond, Washington) and JMP Statistical Discovery from SAS (version 17, Cary, NC). Continuous and ordinal variables are presented with medians and interquartile ranges (IQR). Categorical variables are presented as percentages and numbers.

From 2017 to 2023, there were 8,014,737 encounters within the registry datasets. With the datasets, there were 1,850 pregnant patients that had a documented hysterotomy procedure, of which, 142 hysterotomy procedures with a documented pregnancy status occurred in the ED and met inclusion for this analysis (Table 1). Notably, most included cases survived to hospital discharge (Table 1). Pregnancy cases did not document gestational age except in four cases. CPR was not a documented intervention in 100% of the cases included in this analysis, indicating that the 142 cases represent a mixture of RH and peri-arrest cesarean procedures supporting further studies into the indications and outcomes of both procedures. The median maternal age was 27 years (IQR 22–31, range 16–44), and collisions represented the most common mechanism of injury (77%). There were 86 (61%) cases that went straight from the ED to the operating room (OR). The majority received at least one unit of blood products (Fig. 1). The median time from arrival to procedure start was 25 min (IQR 12–50) with the fastest being immediately upon arrival. There were 125 (88%) cases that had signs of life on arrival. For other resuscitation procedures, there were 48 (34%) cases that were intubated, one (< 1%) that had a resuscitative endovascular balloon occlusion of the aorta (REBOA) placed, 25 (18%) that received CPR, and six (4%) that received a resuscitative thoracotomy. Among the 20 cases with documented prehospital cardiac arrest, two (10%) survived to hospital discharge. Among the 25 cases with documented ED CPR, one (4%) survived to hospital discharge. Among those in the study undergoing RH who had no signs of life on arrival (n = 17), none survived to hospital discharge. Of those, 11 were injured in collisions and six were injured by a firearm, representing the two most common mechanisms of injury (Table 1). Of the 142 included cases, there was one that was first trimester, one that was second trimester, and two that were third trimester; the remainder had pregnancy diagnoses that did not specify gestational age. There were six cases that had a concomitant RH and resuscitative thoracotomy, all of which arrived by emergency medical services (EMS) with half experiencing prehospital arrest (Table 2).

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Table 1. Patient Characteristics

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Table 2. Specific Outcomes of Six Cases Receiving Concomitant Resuscitative Hysterotomy and Resuscitative Thoracotomy

The aim of this study was to examine the incidence of RH in the ED following maternal traumatic injury and compare the maternal outcomes to those presented in other studies. Of the 142 cases meeting criteria for inclusion, most patients survived to hospital discharge. Neonatal survival rate is unknown as the dataset is de-identified including dates, times, and locations limiting the ability to link the maternal encounter to the neonatal encounter within the registry. The high survival to discharge is likely reflective of the substantial number that did not have documented arrest upon arrival nor CPR in the ED, suggesting that many of these may have been peri-arrest rather than during an arrest event. As peri-arrest is not a documented scenario, we are suggesting this as an inference that cannot be directly supported by the available data. Moreover, the delayed time from arrival to performance of the procedure in many cases suggests that additional consultative experts may have been available at the bedside that are more experienced in the procedure than emergency physicians (e.g. obstetricians). To that end, the delayed time also allows for more personnel resources to be allocated so the proceduralist could focus on the procedure rather than the totality of the resuscitation.

Small numbers of documented pre-hospital cardiac arrest and ED CPR suggest that RH was primarily performed in a peri-arrest setting, potentially to avoid cardiac arrest in a decompensating patient, and/or to avoid fetal exposure to hemodynamic instability when viability was retained, probably later than 24 weeks gestation. Aftab et al reported similar data in a smaller cohort (n = 4) with available gestational age data, wherein RH was performed in a peri-arrest setting in 75% of patients, and maternal survival rate was 75%, consistent with data reported here [9]. This suggests that not only can RH be used in the setting of maternal cardiac arrest, but it could also be considered as a preventative intervention in a pregnant patient with impending cardiovascular collapse and may improve survival rates if initiated prior to cardiac arrest.

In the 142 cases examined, the median time between patient arrival and initiation of RH was 25 min, similar to results reported by other studies [10]. It is important to note that, while initiation of RH is recommended within 4–5 min of MCA if ROSC is not obtained, when RH is performed in a peri-arrest scenario, time between patient arrival and initiation of RH far exceeds these recommendations [7]. The extended times presented in our dataset, along with the lack of documentation of the time between cardiac arrest and initiation of RH, suggest that many of the procedures may have been performed in a peri-arrest setting, supporting the findings by Aftab et al of increased survival rates in peri-arrest RH patients [9]. However, the lack of documented time between cardiac arrest and RH initiation in many cases is a limitation within the registry as adverse events (e.g. cardiac arrest) are only binary variables and not timed variables. Moreover, the prehospital arrest variable does not include timing factors such as time from arrest to arrival, nor interventions performed by EMS—all factors that can influence outcomes. Another study reported that surviving RH patients had lower recorded times between cardiac arrest and initiation of RH compared to non-surviving patients, supporting the assertion that decreasing the time between arrest and initiation of RH can improve survival rates [7]. While survival is multifactorial and cannot be exclusively attributed to rapid initiation of RH, time is a factor that can increase the odds of survival in viable patients.

The vast majority of traumatic injuries were due to collisions, consistent with other studies assessing RH in the setting of traumatic MCA or maternal injury (Table 1) [1, 9, 10, 14]. Collisions causing traumatic injuries have additional considerations when pregnant patients are involved, due to the physiological changes and increased blood volume, and the injuries could result in RH following MCA or with impending cardiovascular collapse to prevent MCA [1]. Of the 17 patients showing no signs of life on arrival, 11 (65%) were injured in collisions. Though more severe injuries can be mitigated by proper safety precautions such as the use of a seatbelt, they cannot be prevented in the instance of a collision and often necessitate additional interventions to increase maternal survival [1].

Multiple interventions were employed to increase maternal survival, including transfusion of blood products (Fig. 2). About half of patients received at least one unit of blood products with many receiving large volume transfusions, consistent with postoperative resuscitative challenges (Fig. 2) [19]. In addition to transfusion, RH is also useful for relieving aortocaval compression by the gravid uterus in the maternal system and increasing chances of ROSC [6, 8]. Nearly one-third of patients were intubated as part of the resuscitative efforts, which is a procedure that has been noted to have increased difficulty in pregnant women, and often requires an experienced provider [7, 14]. Due to lack of availability of gestational age data, our interpretations of airway management are limited. Six patients underwent concomitant RH and resuscitative thoracotomy, with half showing signs of life on arrival but none surviving to discharge (Table 2). Four (67%) patients who received concomitant RH and resuscitative thoracotomy were injured in collisions (Table 2). Of those, three received blood products, and all received over 4 units of blood products, indicating that severe collision injuries can result in patients in extremis (Table 2; Fig. 2). These cases represent the true extreme of trauma resuscitation procedures with multiple body cavities being opened in the ED. One instance of REBOA was recorded in the cases examined, consistent with attempts to control hemorrhage. The registry does not capture procedure success nor procedure location, so the zone of REBOA placement remains unknown (e.g., high aortic placement versus low pelvic placement).

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Figure 2. Total 4-h blood products.

Limitations of this study relate to the extent of available data regarding gestational age and time of cardiac arrest. Only four encounters out of 142 specified a gestational age, which introduces a potential information bias in interpreting maternal survival. Accordingly, results were not interpreted in this context to minimize bias. Another component that was largely absent from the analyzed data were the recorded times between cardiac arrest and initiation of RH. As previously suggested, this may indicate that many patients did not arrest prior to RH or it just was not documented. Future studies may pursue investigating the efficacy of RH as a peri-arrest intervention to prevent complete cardiovascular collapse and increase maternal survival. In conjunction with the limitations mentioned here, other studies found similar limitations in data quality and extent of available data, indicating that more rigorous documentation is needed to continually assess and advance existing knowledge on RH. However, given the exceedingly low frequency of this procedure out of more than 8 million total encounters, large, robust datasets with such details will likely never exist.

Conversely, this study presents a large cohort of RH cases and outcomes, both in the setting of MCA and peri-arrest settings. These cases represent a large sample from many different trauma centers, with data from TQIP, a widely accepted gold-standard for trauma registry data.

Despite the significant limitations in the context of available data, we conclude that incidence of RH was rare and was associated with a high risk of maternal mortality. Due to the low rates of documented CPR, and high rates of survival to discharge, peri-arrest cesarean may serve as a valuable intervention to increase maternal survival in the setting of maternal trauma.

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