An anxiety disorder following childbirth that has received increased research attention is Posttraumatic Stress Disorder (PTSD). However, methodological and theoretical problems limit research findings. This thesis identifies these problems, and evaluates research on trauma in childbirth considering these concerns. A primary aim of this thesis was to examine the prevalence of traumatic births and PTSD and partial PTSD (i.e., subsyndromal PTSD) using a methodology that addressed previous limitations. Data were collected during the third trimester and 4 to 6 weeks, 3 months, and 6 months postpartum. Nine hundred and thirty three women completed the first study phase. Results revealed that 45.5% of women experienced a traumatic birth using the DSM-IV criteria for a traumatic event and that 1.2% had PTSD at 4 to 6 weeks and 3.1% had PTSD at 3 and 6 months postpartum respectively. The prevalence rates of partial PTSD ranged from 1.3% to 2.3% postpartum. Another primary aim was to investigate variability in outcome to childbirth specific to perceiving birth as traumatic, developing PTSD and PTSD symptoms, and PTSD symptom change. Few studies have examined the predictive factors of meeting criteria for a traumatic birth or the predictors of PTSD postpartum. Thus, a goal of this thesis was to investigate variation in childbirth outcome, using prebirth, birth, and postbirth factors. Specifically, the thesis investigated the predictors of perceiving childbirth to be traumatic, the development of PTSD and PTSD symptoms, and PTSD symptom change, and found that some of the most salient predictors include: persistent dissociation, environmental stressors, and peritraumatic affective responses such as the intensity of fear, helplessness, and horror. The study was able to correctly predict, using cross-validated data, 88% of women as either meeting or not meeting criteria for a traumatic birth; 87% as developing or not developing PTSD; and 83% as experiencing an improvement or a decline in symptoms. The study also predicted 77% of PTSD symptom severity. Theoretical and practical implications and areas for future research are discussed.