['To examine the effects of prenatal stress on cognition and behavioral fearfulness in infants.', "Mothers were recruited at amniocentesis at Queen Charlotte's and Chelsea Hospital, London, between 2001 and 2005, and recalled when their children were 14 to 19 months to assess cognitive development using the Bayley Scales and fearfulness using the Lab-TAB. Measures of prenatal and postnatal life events and current psychological state were collected at the postnatal visit.", 'Prenatal stress predicted both mental development (rs = -0.39, n = 123 p < .0001) and observed fearfulness (rs = 0.33, n = 106, p < .001); the magnitude of effect was essentially unchanged after covarying postnatal stressors, maternal education and psychological state, exposures to medications and substances during pregnancy, and birth outcomes. Prenatal stress accounted for 17% of the variance in cognitive ability and 10% of the variance in observed fearfulness. The correlation between mental development and fearfulness was minimal (r = -0.06, not significant). Prenatal partner relationship strain accounted for 73.5% and 75.0% of the prenatal stress related variance on infant cognitive and fearfulness scores, respectively.'] Does maternal stress during pregnancy predict cognitive ability and fearfulness in infancy?