The examiners had different proficiency in vaginal ultrasound. As a minimum training to be allowed to include women in the study, the midwives and doctors were trained individually in a defined education program. The education program was based on co-measuring the AVD with one of two experienced experts of AVD-measurement ( ref metodartikeln) . All examiners had to perform co-measurements in at least five women in term pregnancy. Each woman was, after informed consent, measured three times by both the expert and the examiner at education. These women were not included in the present study. The measured AVD values were not shared by the expert and the examiner. The AVD values were compared afterwards, outside the delivery room. In order to be given permission to independently measure the AVD, the examiners had to perform similar values (+/- five mm) as the expert, in five women. Proficiency was achieved among all examiners.