Factors Influencing Pregnant Women's Injuries and Fetal Loss Due to Motor Vehicle Collisions: A National Crash Data-Based Study

Fluid-structure interaction analysis of amniotic fluid with fetus and placenta inside uterus exposed to military blasts

INTRODUCTION

Pregnancy-related trauma is one of the leading causes of morbidity and mortality in pregnant women and fetuses. The fetal response to injury is largely dependent on the timing of fetal presentation and the underlying pathophysiology of the trauma. The optimal management of pregnant patients who have suffered an obstetric emergency depends on clinical assessment and understanding of the placental implantation process, which can be difficult to perform during an emergency. Understanding the mechanisms of traumatic injuries to the fetus is crucial for developing next-generation protective devices.

METHODS

This study aimed to investigate the effect of amniotic fluid on mine blast on the uterus, fetus, and placenta via computational analysis. Finite element models were developed to analyze the effects of explosion forces on the uterus, fetus, and placenta, based on cadaveric data obtained from the literature. This study uses computational fluid-structure interaction simulations to study the effect of external loading on the fetus submerged in amniotic fluid inside of the uterus.

RESULTS

Computational fluid-structure interaction simulations are used to study the effect of external loading on the fetus/placenta submerged in amniotic fluid inside the uterus. Cushioning function of the amniotic fluid on the fetus and placenta is demonstrated. The mechanism of traumatic injuries to the fetus/placenta is shown.

DISCUSSION

The intention of this research is to understand the cushioning function of the amniotic fluid on the fetus. Further, it is important to make use of this knowledge in order to ensure the safety of pregnant women and their fetuses.

Fetal deaths and maternal injury in motor-vehicle crashes using NASS-CDS and CISS field data

OBJECTIVE

This study determined the risk for fetal death and maternal injury in the same sample of motor-vehicle crashes. The frequency and risk of serious injury (MAIS 3 + F) were also assessed by sex, pregnancy, seating position and crash type.

METHOD

The 2008-2015 NASS-CDS and 2017-2020 CISS are representative samples that were analyzed for the risk of fetal death and the risk of maternal injury grouped by MAIS 0-2, MAIS 3 + F and death (F) in 2000+ model year (MY) light vehicles. All electronic cases involving fetal mortality were reviewed for mechanism of injury. Separately, the 2000-2015 NASS-CDS and 2017-2020 CISS data was analyzed for the risk of serious injury for male, female and pregnant female occupants by seating position and crash type in 2000+ MY light vehicles. All calculations are made with weighted data. The significance of differences in risk was determined by the Rao-Scott chi-square test in SAS and z-test for differences in proportions.

RESULTS

There were 2,467 ± 1,407 fetal deaths in light vehicle crashes from 2008-2015 and 2016-2020 with an annual occurrence of 206/yr. The risk for fetal death was 1.25% ± 0.74% of exposed pregnant females. There were 127 ± 67 deaths of pregnant females, or 11/yr in the same sample. The fatality risk was 0.065% ± 0.035%. The difference in proportions was statistically significant (z = 46.1, p < 0.0001). Fetal deaths occurred 19.4-times more often than deaths of pregnant females. In 82.9% of the crashes with a fetal death, the pregnant female was not seriously injured (MAIS 3 + F). The most common mechanism of fetal death was a minor crash, in 80.1% of the weighted cases based on review of photos of the case vehicle and observing very minor structural damage to the vehicle. The minor crash involved either yaw of the occupant compartment with side loading of the pregnant female or her displacement into the restraint system and side interior in 71.7% of the crashes. A severe crash with intrusion at the seating position of the pregnant female occurred in only 11.5% of cases. It usually caused serious injury to the pregnant female and fetal death.

CONCLUSIONS

Fetal deaths occurred 19.4-times more often than deaths of pregnant females in a 12-year sample of motor-vehicle crashes. The most common mechanism was a minor crash that resulted in a fetal death without serious injury to the pregnant female and involved side or oblique loading of the pregnant female.

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.

Comparison of Motor Vehicle Collision Injuries between Pregnant and Non-Pregnant Women: A Nationwide Collision Data-Based Study

We compared the independent predictive factors for moderate and severe injuries, along with characteristics and outcomes of motor vehicle collisions, between pregnant and non-pregnant women. Using 2001–2015 records from the National Automotive Sampling System/Crashworthiness Data System, we selected 736 pregnant women and 21,874 non-pregnant women having any anatomical injuries. Pregnant women showed less severe collisions, fewer fatalities, and less severe injuries in most body regions than non-pregnant women. In pregnant women, the rate of sustaining abbreviated injury scale (AIS) scores 2+ injuries was higher for the abdomen only. For non-pregnant women, rear seat position, airbag deployment, multiple collisions, rollover, force from the left, and higher collision velocity had a positive influence on the likelihood of AIS 2+ injuries, and seatbelt use and force from the rear had a negative influence. There is a need for further development of passive safety technologies for restraint and active safety features to slow down vehicles and mitigate collisions. The influencing factors identified may be improved by safety education. Therefore, simple and effective interventions by health professionals are required that are tailored to pregnant women.