This study aimed to identify factors associated with birth-related post-traumatic stress symptoms during the early postnatal period. Secondary analysis was conducted using data from a prospective cohort study of 1824 women who gave birth in one large hospital in England. Post-traumatic stress symptoms were measured by the Impact of Event Scale at 6 to 8 weeks postpartum. Zero-inflated negative binomial regression models were developed for analyses. Results showed that post-traumatic stress symptoms were more frequently observed in black women and in women who had a higher pre-pregnancy BMI compared to those with a lower BMI. Women who have a history of mental illness as well as those who gave birth before arriving at the hospital, underwent an emergency caesarean section or experienced severe maternal morbidity or neonatal complications also showed symptoms. Women's perceived control during labour and birth significantly reduced the effects of some risk factors. A higher level of perceived social support during the postnatal period also reduced the risk of post-traumatic stress symptoms. From the perspective of clinical practice, improving women's sense of control during labour and birth appears to be important, as does providing social support following the birth.
Keywords: Cohort studies; Post-traumatic stress disorders; Postnatal care; Zero-inflated negative binomial regression.