Effects of seat belts worn by pregnant drivers during low-impact collisions

Severity of Placental Abruption in Restrained Pregnant Vehicle Drivers: Correct Seat Belt Use Confirmed by Finite Element Model Analysis

Despite wearing a seat belt, pregnant drivers often suffer from negative fetal outcomes in the event of motor accidents. In order to maintain the safety of pregnant drivers and their fetuses, we assessed the severity of placental abruption caused by motor vehicle collisions using computer simulations. We employed a validated pregnant finite element model to determine the area of placental abruption. We investigated frontal vehicle collisions with a speed of 40 km/h or less involving restrained pregnant drivers with a gestational age of 30 weeks. For a crash speed of 40 km/h, the placental abruption area was 7.0% with a correctly positioned lap belt across the lower abdomen; it was 36.3% with the belt positioned at the umbilicus. The area of placental abruption depended on collision speed, but we found that with a correctly positioned belt it likely would not lead to negative fetal outcomes. We examined the effects on placental abruptions of reconfiguring seat belt width and force limiter setting. A wider lap belt and lower force limiter setting reduced the area of placental abruption to 3.5% and 1.1%, respectively; however, they allowed more forward movement upon collision. A 2.5 kN force limiter setting may be appropriate with respect to both forward movement and reduced placental abruption area. This study confirmed the importance of correctly using seat belts for pregnant drivers. It provides valuable evidence about improving safety equipment settings.

Comparison of the Injury Mechanism between Pregnant and Non-Pregnant Women Vehicle Passengers Using Car Crash Test Dummies

This paper analyzes the kinematics and applied forces of pregnant and non-pregnant women dummies sitting in the rear seat during a frontal vehicle collision to determine differences in the features of abdominal injuries. Sled tests were conducted at 29 and 48 km/h with pregnant and non-pregnant dummies (i.e., MAMA IIB and Hybrid III). The overall kinematics of the dummy, resultant acceleration at the chest, transrational acceleration along each axis at the pelvis, and loads of the lap belt and shoulder belt were examined. The belt loads were higher for the MAMA IIB than for the Hybrid III because the MAMA IIB had a higher body mass than the Hybrid III. The differences in the lap belt loads were 1119 N at 29 km/h and 1981-2365 N at 48 km/h. Therefore, for restrained pregnant women sitting in the rear seat, stronger forces may apply to the lower abdomen during a high-velocity frontal collision. Our results suggest that for restrained pregnant women sitting in the rear seat, the severity of abdominal injuries and the risk of a negative fetal outcome depend on the collision velocity.

Factors Affecting the Severity of Placental Abruption in Pregnant Vehicle Drivers: Analysis with a Novel Finite Element Model

We clarified factors affecting the severity of placental abruption in motor vehicle collisions by quantitively analyzing the area of placental abruption in a numerical simulation of an unrestrained pregnant vehicle driver at collision velocities of 3 and 6 m/s. For the simulation, we constructed a novel finite element model of a small 30-week pregnant woman, which was validated anthropometrically using computed tomography data and biomechanically using previous examinations of post-mortem human subjects. In the simulation, stress in the elements of the utero–placental interface was computed, and those elements exceeding a failure criterion were considered to be abrupted. It was found that a doubling of the collision velocity increased the area of placental abruption 10-fold, and the abruption area was approximately 20% for a collision velocity of 6 m/s, which is lower than the speed limit for general roads. This result implies that even low-speed vehicle collisions have negative maternal and fetal outcomes owing to placental abruption without a seatbelt restraint. Additionally, contact to the abdomen, 30 mm below the umbilicus, led to a larger placental abruption area than contact at the umbilicus level when the placenta was located at the uterus fundus. The results support that a reduction in the collision speed and seatbelt restraint at a suitable position are important to decrease the placental abruption area and therefore protect a pregnant woman and her fetus in a motor vehicle collision.

Predictive risk factors of adverse perinatal outcomes following blunt abdominal trauma in pregnancy

BACKGROUND

The primary objective was to identify predictive risk factors of preterm delivery following blunt abdominal trauma. The secondary objective was to identify risk factors of other adverse outcomes, Neonatal Intensive Care Unit (NICU) admission, placental abruption, fetal demise, and Cesarean Delivery (CD).

METHODS

This retrospective study included pregnant patients with gestational age (GA) ≥23 weeks who presented after blunt abdominal trauma to Richmond University Medical Center from October 2015 to January 2020. Patients were identified using the following diagnostic International diagnostic classification (ICD-10) codes: O9A.212, O9A.213, and 071.89, and excluded if trauma did not involve the abdomen, penetrating, <23 weeks, or incomplete records. Collected data points included maternal demographic factors, clinical laboratory values, maternal clinical findings at presentation, abdominal ultrasound, results of fetal monitoring, Abbreviated Injury Score (AIS) for abdomen, and Injury Severity Score (ISS). Univariate analyses were compared using the Student's t-test or Mann-Whitney U-test. Categorical data were compared using the chi-squared test or Fisher's exact test with P-value < .05 as significant.

RESULTS

154 patients were included in the final analysis. The incidence of the primary outcome, preterm delivery before 37 weeks, was 11.0% (17/154). The incidence of secondary outcomes following blunt abdominal trauma were abruption 0% (0/154), fetal demise 0.6% (1/154), CD 44% (68/154), NICU admission 24% (37/154). Maternal demographic factors, presence of uterine contractions, maternal clinical conditions (abdominal pain, abdominal tenderness, vaginal bleeding), hematologic and coagulation studies, ultrasound findings, fetal heart rate tracing category, AIS score for abdomen, and ISS score were not predictive of preterm delivery or other secondary outcomes.

CONCLUSION

The incidence of adverse maternal and neonatal outcomes is low following blunt abdominal trauma. Extended monitoring of asymptomatic patients including laboratory tests and coagulation profiles were not predictive of preterm labor or secondary adverse perinatal outcomes.

LEVEL OF EVIDENCE

Therapeutic/Care management, Level III.

Trauma in Pregnancy

One of the most common causes of obstetric morbidity and mortality is trauma in pregnancy. Several maternal physiological changes during pregnancy have a significant impact on the mechanism, presentation, and management of trauma in this population. It is crucial for health providers dealing with trauma to know and understand these differences between pregnant and nonpregnant patients. The obstetric trauma patient requires a multidisciplinary approach, including obstetrics, maternal fetal medicine, anesthesiology, surgery, and intensive care teams. The aim of this article is to review the most updated information on trauma during pregnancy.

Mechanisms of Negative Fetal Outcome in Frontal Vehicle Colli-Sions Involving Unbelted Pregnant Drivers

To determine the cause of negative fetal outcomes and the causative mechanism in a frontal collision, we analyzed the kinematics and mechanisms of injuries using an unbelted pregnant dummy, the Maternal Anthropometric Measurement Apparatus dummy, version 2B. Sled tests were performed to recreate frontal impact situations with impact speeds of 13, 26, and 40 km/h. Overall kinematics of the dummy were examined through high-speed video imaging. Quantitative dummy responses-such as time courses of the abdominal pressure, chest deflection, neck injury criteria (Nij), and displacement of the pelvis during impact-were also measured. The maximum abdominal pressure of 103.3 kPa was obtained at an impact speed of 13 km/h. The maximum chest deflection of 38.5 mm and Nij of 0.36 were obtained at an impact speed of 26 km/h. The highest maximum chest deflection of >40.9 mm, Nij of 0.61, and forward pelvis displacement of 478 mm were obtained at an impact speed of 40 km/h. Although the kinematics and mechanism of injuries of the dummy were different for different collision speeds, we found that unbelted pregnant drivers suffer severe or fatal injuries to the fetus even in low-speed collisions.

Education for appropriate seatbelt use required for early-phase pregnant women drivers

Considerable numbers of pregnant women do not understand the correct way to use seatbelts; thus, they are inappropriately restrained when wearing seatbelts. To improve appropriate seatbelt wearing by pregnant women vehicle passengers, we examined their use by pregnant women drivers and the independent factors influencing appropriate use. We undertook a cross-sectional survey of 1,000 pregnant women in Shiga Prefecture, Japan. Among 774 returned questionnaires, we analysed those of 680 pregnant women who always wore a seatbelt. The mean participant age was 31.4 ± 5.0 years and mean gestational age 26.2 ± 8.2 weeks; 97.7% of subjects always wore a seatbelt; 86.9% wore a seatbelt correctly and 13.1% incorrectly. Multivariate analysis indicated that receiving information about correct seatbelt use (odds ratio, 2.25; P < 0.005) and gestational age (odds ratio, 1.06; P < 0.001) were significant independent factors for correct seatbelt use. Providing information about correct seatbelt use during the early term is required for pregnant women to protect both the mother and fetus.

Analysis of restraint use in pregnant versus non-pregnant populations involved in motor vehicle collisions

BACKGROUND

Traumatic injuries obtained by pregnant females in motor vehicle collisions present unique treatment challenges for trauma and orthopaedic surgeons. Understanding safety choices in this population can help physicians and public safety advocates in delivering effective and targeted safety messages.

METHODS

A publicly available, de-identified national data set that documents crash information (NASS-CDS) was examined to identify cohorts of pregnant and non-pregnant vehicle occupants and regression analysis employed to identify factors associated with belt non-use.

RESULTS

Pregnant women were found to have significantly lower rates of belt use compared to non-pregnant females (70.0% vs. 90.3%, Rao-Scott Sample Weighted Chi-Square p = 0.0265). Logistic regression identified younger age and sitting in the back seat as associated with lower rates of belt use.

CONCLUSION

Pregnant women wear belts at significantly lower frequencies than non-pregnant women and youth and second row seating increase noncompliance rates. This work suggests the need for targeted intervention strategies to improve belt compliance.

Chest compression of a pregnant woman by a seatbelt might affect fetal outcome, even in minor to moderate frontal vehicle collisions

INTRODUCTION

Pregnant women often suffer from negative fetal outcomes, despite wearing a seatbelt correctly. When restrained vehicle passengers are involved in a frontal collision without suffering from any injuries, the forces they experience are particularly concentrated in the chest because of the seatbelt. We analyzed the biomechanics of chest injuries sustained by restrained pregnant drivers and possible effects of these injuries on the fetus.

MATERIAL AND METHODS

The Maternal Anthropometric Measurement Apparatus dummy, version 2B, representing a pregnant woman at 30 weeks of gestation, was used. Sled tests were performed for recreating frontal impact situations with vector velocity changes at impact speeds of 13, 26, and 40km/h. Overall kinematics of the dummy were examined using high-speed video imaging. Quantitative dummy responses, such as time course of acceleration of the sled and chest, pressure of the belt, and deflection of the chest (right and left) during impact were also measured.

RESULTS

Although collision velocities were different, the distances of forward movement of the dummy were similar (121-129mm) owing to the safety devices. However, maximum deflection of the chest (35.4mm to the left and 15.7mm to the right) was obtained at a 26-km/h collision. Additionally, maximum deflection of 28.7mm to the left and 10.9mm to the right of the chest were obtained at 40km/h.

CONCLUSIONS

Because the uterus enlarges and the fundus reaches the lower part of the rib cage during late pregnancy, we consider that the reason for negative fetal outcomes is partly owing to chest compression and subsequent applied forces on the uterus, even in minor to moderate frontal collisions. This knowledge may be useful for forensic scientists who determine the causes and mechanisms of a fetal death or the offenders' responsibilities for both maternal and fetal outcomes when the mother is involved in a frontal vehicle collision.

Shorter pregnant women restrained in the rear seat of a car are at risk for serious neck injuries: Biomechanical analysis using a pregnant crash test dummy

INTRODUCTION

When considering seat belt contacts to the neck in pregnant woman of shorter height sitting in the rear seat of a vehicle, subsequent injuries after a collision must be understood in the context of both maternal and fetal outcomes. To determine likely injuries to a pregnant woman sitting in the rear seat, we determined the kinematics of a "pregnant" crash test dummy by measuring neck compression forces and biomechanical parameters acting on the head and neck.

METHODS

Sled tests using a shorter-height pregnant woman crash test dummy (Maternal Anthropometric Measurement Apparatus, ver. 2B) were performed at the HYGE sled test facility representing full frontal impact at target velocities of 29km/h and 48km/h. Kinematics of the dummy and biomechanical parameters of the head, neck, and chest were measured. Pressure to the neck was measured using Prescale (Fujifilm, Tokyo, Japan).

RESULTS

During frontal collision tests, the shoulder belt compressed the neck at a pressure >12.8MPa, even during the low-velocity impact. In addition to neck flexion, right side bending and the head and chest moving in opposite directions were observed, with maximum differences of 42.4mm at high velocity and 33.7mm at low velocity.

CONCLUSIONS

This study provides data on the kinematics of pregnant women of short height sitting in the rear seat during a frontal collision using a pregnant woman crash test dummy. The knowledge gathered from this study should be useful for determining pregnant women passengers' kinematics at the time of collision and evaluating the relationship between the vehicle collision and fetal outcomes.

Trauma in pregnancy: A review of the Pennsylvania Trauma Systems Foundation database

Objective

The goal of this study is to determine if injury severity score (ISS) of ≥9 and systolic blood pressure (SBP) predict poor maternal/pregnancy outcomes in blunt and penetrating trauma, respectively.

Methods

The Pennsylvania Trauma Systems Foundation database was used to identify pregnant trauma patients. Blunt trauma patients were analyzed with regard to ISS, while penetrating trauma patients were analyzed to determine whether SBP < 90 mmHg was predictive of poor maternal outcome.

Results

Patients with severe blunt injury (ISS ≥ 9) due to motor vehicle accident were less likely to wear seatbelts (51% vs. 63%, p = 0.005), and delivery was required in 17% of these patients as compared to 6% of the less severely injured, and only 6% of those were vaginal deliveries. Severely injured patients were discharged home 68% of the time and 6% died compared to less severely injured patients of which 83% were discharged home and <1% died; all other patients required discharge to a rehabilitation facility. Patients with penetrating trauma and SBP < 90 mmHg on arrival were more likely to require delivery (35% vs. 5%, p < 0.001) and were 14 times more likely to die (58% vs. 4%, p < 0.001) when compared to the normotensive group.

Conclusion

ISS ≥ 9 and SBP < 90 mmHg are predictors for poor outcomes after trauma during pregnancy. Severely injured blunt trauma patients often require surgery and delivery. Patients who present with SBP < 90 after penetrating trauma are more likely to deliver and are 14 times more likely to die.

Pregnancy and childbirth: What changes in the lifestyle of women who become mothers?

Pregnancy is a period influenced by the interaction of several factors, therefore this study aimed to identify changes in lifestyles due to pregnancy and childbirth in Portuguese and immigrant women in Portugal. This is a qualitative study, using the semi-structured interview, with eighty-two Portuguese and immigrant women. Content analysis was used, with verbatim classification supported by Nvivo 10. It was authorized by an Ethics Commission. Results revealed that the primary changes in lifestyles due to pregnancy were in eating habits (nutrition), daily activity, exposure to danger, sleep and rest patterns, social and family relationships, going out, self-care, work, clothing and footwear, travel, health monitoring and sexual activity and substances consumption. The main change after the birth, manifested by these women, was that their lives began to revolve around their baby.

Trauma in pregnancy: an updated systematic review

We reviewed recent data on the prevalence, risk factors, complications, and management of trauma during pregnancy. Using the terms "trauma" and "pregnancy" along with specified mechanisms of injury, we queried the PubMed database for studies reported from Jan. 1, 1990, through May 1, 2012. Studies with the largest number of patients for a given injury type and that were population-based and/or prospective were included. Case reports and case series were used only when more robust studies were lacking. A total of 1164 abstracts were reviewed and 225 met criteria for inclusion. Domestic violence/intimate partner violence and motor vehicle crashes are the predominant causes of reported trauma during pregnancy. Management of trauma during pregnancy is dictated by its severity and should be initially geared toward maternal stabilization. Minor trauma can often be safely evaluated with simple diagnostic modalities. Pregnancy should not lead to underdiagnosis or undertreatment of trauma due to unfounded fears of fetal effects. More studies are required to elucidate the safest and most cost-effective strategies for the management of trauma in pregnancy.

Motor vehicle safety during pregnancy

Motor vehicle crashes during pregnancy are the leading cause of traumatic fetal mortality and serious maternal injury morbidity and mortality in the United States, injuring approximately 92,500 pregnant women each year. Little is known about the circumstances surrounding these crash events and the maternal characteristics that may increase women's vulnerability to crash-related injuries during pregnancy. Even less is known about the effects of crashes on fetal outcomes. Crash simulation studies using female anthropomorphic test devices and computational models have been conducted to better understand the mechanisms of maternal and fetal injuries and death resulting from motor vehicle crashes. In addition, several case reports describing maternal and fetal outcomes following crashes have been published in the literature. Only a few population-based studies have explored the association between motor vehicle crashes and adverse maternal and/or fetal outcomes and even fewer have examined the effectiveness of seat belts and/or airbags in reducing the risk of these outcomes. This paper reviews what is presently known about motor vehicle crashes during pregnancy, their effects on maternal and fetal outcomes, and the role of vehicle safety devices and other safety approaches in mitigating the occurrence and severity of maternal crashes and subsequent injuries. In addition, this paper suggests interventions targeted towards the prevention of crashes during pregnancy.