We investigated the relationship between the stress of a high-risk birth and the development of symptoms of posttraumatic stress disorder in mothers. Six measures of perinatal stressors (gestational age of the baby, birth weight, length of hospital stay for the baby, a postnatal complications rating for the infant, and Apgar scores at 1 and 5 minutes) were used to predict the frequency of posttraumatic stress symptoms. Severity of infant complications, gestational age, and length of stay accounted for 35% of the variance in reports of posttraumatic stress symptoms. Both mothers of premature infants and mothers of term infants hospitalized in a neonatal intensive care unit reported significantly more symptoms of posttraumatic stress than mothers of healthy term infants (p < 0.01). We conclude that the birth of an infant at high risk, especially one with severe medical complications, can have long-term emotional consequences for the baby's mother.