We consider the effects of major prenatal economic shocks experienced by mothers on two indicators of newborn-infant health, birth weight and head circumference, using detailed microdata from the UK ALSPAC survey. Controlling for physiological and socioeconomic factors, an economic shock in the first 18 weeks of gestation lowers birth weight by 40–70 g and head circumference by 2–3 mm. We find evidence of transmission via poorer maternal health due to absolute material deprivation and tobacco and alcohol consumption, but not for the endocrinological effects of increased psychosocial anxiety. The fragile-male hypothesis holds for birth weight but not for head circumference, as predicted by recent theories on gender differences in prenatal development.