Pregnant Occupant Research Articles

Computational pregnant occupant model, ‘Expecting’, for crash simulations

A computational model of the pregnant occupant, which is capable of simulating the dynamic response to acceleration impacts, is introduced. The occupant model represents a 5th percentile female at around the 38th week of pregnancy. A finite element uterus and multi-body fetus is integrated into an existing female model to incorporate pregnant female anthropometry. The complete model, ‘Expecting’, is used to simulate a range of frontal impacts of increasing severity from 15km/h to 45km/h. Three levels of occupant restraint, completely unrestrained, three-point seat belt, and three-point seat belt with an airbag, are investigated. The strains developed in the uterus because of loading from the seat belt and steering-wheel unit are presented, together with an analysis of stress distribution due to inertial loading of the fetus on the uterus. The unrestrained cases are shown to be the most dangerous to the fetus, owing to the large interaction with the vehicle steering wheel at the level of the placenta. The use of a three-point seat belt together with a driver airbag appears to offer the greatest protection to the fetus.

'Expecting': occupant model incorporating anthropometric details of pregnant women

This study reports the research for a design tool related to pregnant women's safety during car travel. Anthropometric measurements are taken to generate an occupant model incorporating pregnancy related changes. These anthropometric changes mean that a pregnant occupant may be excluded by the designs, based upon non-pregnant female anthropometry. The paper explains the generation of a comprehensive parametric computer aided model of a pregnant occupant, 'Expecting'. The model can represent different size pregnant occupants as well as the size differences occurring in standing and seated postures. This model can be used as a design tool for automotive designers to help ensure that vehicle designs can accommodate the anthropometric needs of pregnant occupants.

Dynamic tensile properties of human placenta

Automobile crashes are the largest cause of injury death for pregnant females and the leading cause of traumatic fetal injury mortality in the United States. Computational models, useful tools to evaluate the risk of fetal loss in motor vehicle crashes, are based on a limited number of quasi-static material tests of the placenta. This study presents a total of 20 dynamic uniaxial tensile tests on the maternal side of the placenta and 10 dynamic uniaxial tensile tests on the chorion layer of the placenta. These tests were completed from 6 human placentas to determine material properties at a strain rate of 7.0 strains/s. The results show that the average peak strain at failure for both the maternal portion and the chorion layer of the placenta are similar with a value of 0.56 and 0.61, respectively. However, the average failure stress for the chorion layer, 167.8 kPa, is much higher than the average failure stress for the placenta with the chorionic plate removed, 18.6 kPa. This is due to differences in the structure and function of these layers in the placenta. In summary, dynamic loading data for the placenta have been determined for use in computational modeling of pregnant occupant kinematics in motor vehicle crashes. Moreover the computational model should utilize the material properties for the placenta without the chorion layer.

Fetal Outcome in Motor-Vehicle Crashes: Effects of Crash Characteristics and Maternal Restraint

Objective This project was undertaken to improve understanding of factors associated with adverse fetal outcomes of pregnant occupants involved in motor-vehicle crashes. Study Design In-depth investigations of crashes involving 57 pregnant occupants were performed. Maternal and fetal injuries, restraint information, measures of external and internal vehicle damage, and details about the crash circumstances were collected. Crash severity was calculated using vehicle crush measurements. Chi-square analysis and logistic regression models were used to determine factors with a significant association with fetal outcome. Results Fetal outcome is most strongly associated with crash severity ( P P = .002). Proper maternal belt-restraint use (with or without airbag deployment) is associated with acceptable fetal outcome (odds ratio=4.5, P = .033). Approximately half of fetal losses in motor-vehicle crashes could be prevented if all pregnant women properly wore seat belts. Conclusion Higher crash severity, more severe maternal injury, and lack of proper seat belt use are associated with a higher risk of adverse fetal outcome. These results strongly support recommendations that pregnant women use properly positioned seatbelts.

Fetal outcome in motor-vehicle crashes: effects of crash characteristics and maternal restraint

This project was undertaken to improve understanding of factors associated with adverse fetal outcomes of pregnant occupants involved in motor-vehicle crashes. In-depth investigations of crashes involving 57 pregnant occupants were performed. Maternal and fetal injuries, restraint information, measures of external and internal vehicle damage, and details about the crash circumstances were collected. Crash severity was calculated using vehicle crush measurements. Chi-square analysis and logistic regression models were used to determine factors with a significant association with fetal outcome. Fetal outcome is most strongly associated with crash severity (P < .001) and maternal injury (P = .002). Proper maternal belt-restraint use (with or without airbag deployment) is associated with acceptable fetal outcome (odds ratio = 4.5, P = .033). Approximately half of fetal losses in motor-vehicle crashes could be prevented if all pregnant women properly wore seat belts. Higher crash severity, more severe maternal injury, and lack of proper seat belt use are associated with a higher risk of adverse fetal outcome. These results strongly support recommendations that pregnant women use properly positioned seatbelts.

Design guidelines for pregnant occupant safety

During pregnancy a woman's body undergoes a considerable change in size and shape, and this can impact upon her safety during car travel. The two main issues are proper seat belt use and positioning, and steering wheel clearance. A comprehensive analysis of the questionnaire responses by pregnant women and anthropometric measurements demonstrates that the difficulties experienced can be explained by the physical changes and interactions throughout the body during gestation. Analysis of the anthropometry of pregnant women highlights that many pregnant users could easily be excluded from designs inadvertently if the design is based on males or non-pregnant females. Thus incorporation of pregnant women's anthropometry into automotive design could reduce the exclusion rates and alleviate problems. This paper presents guidelines for the automotive industry generated from experiences and anthropometry of pregnant women, with the aim of improving safety for pregnant car occupants.

Designing for safety during pregnancy through a system for automotive engineers

Pregnant women in the UK are legally required to wear seatbelts both as drivers and passengers. This paper considers fitting the seat belt correctly around the pregnant woman's altered body and explores the ways of providing data to automotive engineers. The paper presents the difficulties experienced during pregnancy resulting from women's altered shape and size. Accommodation of pregnant occupant anthropometry is key to improving seat belt use and positioning. An anthropometry website is presented with the aim of enhancing pregnant women's quality of life through an improved seat belt design. The website has been designed to suit the needs of automotive designers and engineers to encourage them to consider pregnant occupant protection.

The effects of uterine ligaments on fetal injury risk in frontal automobile crashes

A finite element model of a seven-month pregnant uterus was created and integrated into a multibody human model. The pregnant occupant model was validated using known abdominal response corridors. Tests of occupants with no restraint, a three-point belt and a three-point belt plus airbag at 35 km/h were simulated to evaluate the effects of four support ligaments connected to the uterus. The primary injury predictor, the peak uterine strain on the anterior uterus, was not found to change appreciably by the absence of the support ligaments; however, high local stress concentrations were found at the ligament attachment sites. Based on these results, it is recommended that computational models of the pregnant occupant contain the supporting ligaments since the stress concentrations may result in increased injury risk in other test configurations or loading conditions.

Computational model of the pregnant occupant: predicting the risk of injury in automobile crashes

OBJECTIVE: The goal of this study was to create a computational model of the pregnant occupant of a motor vehicle to predict fetal outcome in crashes. STUDY DESIGN: A finite element uterine model of a 7-month pregnant woman was created and integrated into a multibody human model. Unrestrained, three-point belt, and three-point belt plus airbag tests were simulated at speeds that ranged from 13 to 55 km per hour. RESULTS: Peak uterine strain, as determined by the model, correlated well with the risk of fetal death, as determined by investigations of car crashes. The strain in the uterine wall exceeded the limits of the tissue in simulations of no restraint at 35 km per hour and three-point belt tests at 45 and 55 km per hour. The safest restraint for the pregnant driver is the combination three-point belt and airbag. CONCLUSION: The model is a good first step toward the prediction of the risk of fetal death and verified experimental findings that note the importance of proper restraint use for the pregnant occupant.

Overview of atmospheric ionizing radiation (AIR) Research: SST-present

The Supersonic Transport (SST) program proposed in 1961, first raised concern for the exposure of pregnant occupants by solar energetic particles (SEP), and neutrons were suspected to have a main role in particle propagation deep into the atmosphere. An eight-year flight program confirmed the role of SEP as a significant hazard and of the neutrons as contributing over half of the galactic cosmic ray exposures, with the largest contribution from neutrons above 10 MeV. The FAA Advisory Committee on the Radiobiological Aspects of the SST provided operational requirements. The more recent lowering of ICRP-recommended exposure limits 1990 with the classification of aircrew as “radiation workers” renewed interest in GCR background exposures at commercial flight altitudes and stimulated epidemiological studies in Europe, Japan, Canada and the USA. The proposed development of a High Speed Civil Transport (HSCT) required validation of the role of high-energy neutrons, and this resulted in ER-2 flights at solar minimum June 1997 and studies on effects of aircraft materials on interior exposures. Recent evaluation of health outcomes of DOE nuclear workers resulted in legislation for health compensation in year 2000 and recent European aircrew epidemiological studies of health outcomes bring renewed interest in aircraft radiation exposures. As improved radiation models become available, it is imperative that a corresponding epidemiological program of US aircrew be implemented.

Characteristics of pregnant women in motor vehicle crashes

Objectives: Motor vehicle crashes are the leading cause of hospitalized trauma during pregnancy. Maternal injury puts the fetus at great risk, yet little is known about the incidence, risks, and...