A 36-year-old woman with a history of one previous caesarean section presented to the birthing suite of a regional hospital with spontaneous rupture of membranes at 39+2/40 weeks. Syntocinon was administered to initiate uterine contractions in the absence of labour, as the patient desired vaginal birth. A caesarean section was subsequently indicated and ergometrine was administered for uterine atony. The patient immediately developed atrial fibrillation (AF). AF is the most common sustained arrhythmia in the general population, but is rare in the obstetric population. AF occurring in an intrapartum setting following the administration of syntocinon and ergometrine, is not documented in the literature. We suggest the initiation of paroxysmal AF was precipitated by an abrupt alteration in autonomic tone caused by administration of syntocinon followed by ergometrine.