The present study examined social comparison processes in 147 pregnant women at high risk of incurring an adverse birth outcome such as fetal loss or preterm delivery. These women typically undergo physical and psychological changes which elevate uncertainty and distress. Theoretically derived hypotheses concerning the impact of threat, self-esteem, perceived control, age, and gravidity (previous pregnancy) on social comparison were tested. Women experiencing low pregnancy-related threat and those with higher self-esteem were more likely to compare themselves favorably to other pregnant women. Younger women who had not been pregnant before compared most frequently; comparisons of physical state were more common than comparisons of emotional well-being or interpersonal relationships. Results are contrasted with social comparison processes in other populations facing stressful life events.