Our study aimed to assess the prevalence of post-traumatic stress disorder (PTSD) after childbirth one year after vaginal delivery and to identify characteristics of women and deliveries associated with it. Questionnaires were mailed a year after delivery to 1103 women with prospectively collected delivery and postpartum data, including a question on day 2 assessing their experience of childbirth. PTSD was assessed a year later by the Impact of Event and Traumatic Event Scales; 22 women (4.2%, 95%CI 2.7-6.3%) met the PTSD diagnostic criteria and 30 (5.7%; 95%CI 3.9-8.0%) PTSD profile criteria. Factors associated with higher risk of PTSD profile were previous abortion (aOR 3.6, 95%CI 1.4-9.3), previous postpartum hemorrhage (Aor 5.3, 95%CI 1.3-21.4), and postpartum hemoglobin <9 g/dl (aOR 2.7, 95%CI 1.0-7.5). Among 56 women (10.3%) reporting bad childbirth memories at day 2 postpartum, 11 (21.1%) met PTSD diagnosis and 11 (21.1%) PTSD profile criteria a year later, compared with 11 (2.4%) (P < 0.001) and 18 (3.8%) (P < 0.001), respectively, of the 489 (87.7%) women with good memories. PTSD is not rare at one year after vaginal delivery in a low-risk population. A simple question at day 2 post partum may identify women most at risk of PTSD and help determine if early intervention is needed.