Using natural disasters to study prenatal maternal stress in humans.

Animal studies of prenatal maternal stress permit random assignment of pregnant animals to stress and no-stress groups, and allow total control of the type, severity, and timing of the stressor in utero. Human studies have obvious constraints that make the use of experimental methods nearly impossible. Studying pregnant women who experience natural disasters during pregnancy, however, approximates the random assignment to groups enjoyed by animal studies, and can characterize the timing of the stressor in utero with great precision. In this chapter, we briefly describe our three ongoing prospective longitudinal studies of children exposed to prenatal maternal stress from natural disasters. We present results from Project Ice Storm in detail, showing effects of prenatal maternal stress on cognitive and neurodevelopment. We contrast these results with preliminary findings from the Iowa Flood Study and introduce the QF2011 Queensland Flood Project. In the "Discussion" section, we present conclusions to date and discuss the relative effects of the severity of maternal objective disaster exposure and maternal subjective distress levels, the moderating effects of fetal sex and the timing of the stressor in utero, and the longevity of the effects. Finally, we discuss some possible mechanisms that may mediate the effects of prenatal maternal stress on the neurodevelopment of children.