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.