Using national datasets and applying plausible assumptions about rates of pregnancy and traffic fatalities, Evans and Redelmeier, the President Emeritus and North America Regional Director estimated the number of fetuses killed per year in traffic crashes in the USA. Two main assumptions were: (1) pregnant and non-pregnant women of the same age have equal chances of becoming traffic fatalities; (2) the death of a pregnant woman leads to the death of her unborn child. They computed that 227 pregnant women died in US traffic in 2012, implying also 227 fetus deaths. This contrasts with 60 babies aged less than one year killed in traffic crashes in 2012, equivalent to 45 deaths in the nine month period corresponding to pregnancy. Thus the risk of fetal death during pregnancy is 227/45 = 5.04 times the risk after birth for equal exposure times. This ratio likely underestimates the disparity because the risk of crashing increases during pregnancy, and the 5.04 ratio ignores the many cases in which the mother survives but the fetus does not.
Complete text at http://www.scienceservingsociety.com/p/200.pdf