There exists considerable research on the effects of prenatal maternal stress on offspring. Animal studies, using random assignment to experimental and control groups, demonstrate the noxious effects of prenatal maternal stress on physical, behavioural and cognitive development. The generalizability of these results to humans is problematic given that cognitive attributions moderate reactions to stressors. In humans, researchers have relied upon maternal anxiety or exposure to life events as proxies for the stressors used with animals. Yet, the associations between maternal anxiety or potentially non-independent life events and problems in infants are confounded by genetic transmission of temperament from mother to child. We summarize the literature on prenatal maternal stress and infant cognitive development, leading to the conclusion that the human literature lacks the ability to separate the effects of the objective exposure to a stressor and the mother's subjective reaction. We then describe our prospective Project Ice Storm in which we are following 150 children who were exposed in utero to a natural disaster. We demonstrate significant effects of the objective severity of exposure on cognitive and language development at age two years with important moderating effects of the timing during pregnancy. The implications of our findings are discussed.

An adverse environment in utero, including exposure to prenatal maternal stress (PNMS), can result in poor birth outcomes such as low birth weight, which increases risk of later cardiometabolic diseases such as hypertension and obesity. It is unclear to what extent PNMS influences obesity risk independent of its impact on birth characteristics, especially among humans. Our objective was to determine whether PNMS resulting from a natural disaster influenced risk of childhood obesity. Eight children with high objective PNMS exposure (14.5%) were obese compared to one child (1.8%) with low exposure (P = 0.02). Objective PNMS increased obesity risk (model 1, P = 0.02, odds ratio = 1.37) after controlling for other potential risk factors. Results suggest that PNMS might be an independent risk factor in the development of childhood obesity. Participants included 111 women who were pregnant during the January 1998 Québec Ice Storm or who conceived within the following 3 months and their children. We tested associations between objective and subjective PNMS from the storm and childhood obesity status at age 5½, controlling for children’s birth characteristics and breastfeeding status; household socioeconomic status; maternal obstetric complications, life events and smoking during pregnancy, psychological functioning, and height (model 1, n = 111) or BMI (for a subset of 69 participants, model 2).