We present the case of a changing Mallampati score during the course of labour in a healthy primigravida. On admission to hospital, the airway was assessed as Mallampati class I-II. At 5 cm cervical dilation, the woman began to bear down strenuously and continued this despite being advised of the inherent hazard. At 8 cm dilation, Caesarean delivery was contemplated because of fetal heart rate decelerations. Repeat airway evaluation revealed marked oedema of the lower pharynx giving rise to a Mallampati score of III-IV. Improvement of the fetal heart rate tracing permitted vaginal delivery under local infiltration. Postpartum, the Mallampati score was still III-IV. However, 12 hr later it had returned to the admission classification of I-II. We recommend that, in addition to the usual airway evaluation on admission, the assessment be repeated in the obstetric patient before induction of general anaesthesia.