Birth-related posttraumatic stress symptoms (PTSS) place a significant burden on mothers and their families. The aim was to (1) identify differential profiles of maternal birth-related PTSS; (2) determine the predictive value of established risk factors; (3) examine comorbidity patterns related to depression and anxiety symptoms. As part of the Norwegian Ahus Birth Cohort, 2,088 (expectant) mothers completed self-report questionnaires from 17 weeks of gestation to 2 years postpartum. The Impact of Event Scale was used to assess PTSS 8 weeks after birth. Latent class analysis revealed four latent classes: a High birth-related PTSS class (4%), a Moderate birth-related PTSS class (16%) particularly characterized by endorsement of intrusion symptoms, a Mild birth-related PTSS class (47%), as well as a No birth-related PTSS class (33%). We found similar (younger age, worse subjective birth experience, higher fear of childbirth) and differential predictors (prior posttraumatic stress disorder, lower education, birth complications). Women classified with High, Moderate, or Mild birth-related PTSS showed higher depression and anxiety symptoms compared to women with No birth-related PTSS. A considerable number of mothers experienced birth-related PTSS, most on a subclinical level, but these women still showed signs of mental distress 2 years postpartum, calling for more universal prevention approaches.