BACKGROUND: the incidence of obesity increases in all developed countries to frightful percentages, also in women of reproductive age. Maternal obesity is associated with important obstetrical complications; and this group also exhibits a higher incidence of prolonged pregnancies and labours. OBJECTIVE: to review the literature on the pathophysiology of onset and progression of labour in obese woman and translate this knowledge into practical recommendations for clinical management. METHODS: a literature review, in particular a critical summary of research, in order to determine associations, gaps or inconsistencies in this specific but limited body of research. FINDINGS: the combination of a higher incidence of post-term childbirths and increased inadequate contraction pattern during the first stage of labour suggests an influence of obesity on myometrial activity. A pathophysiologic pathway for altered onset and progression of labour in obese pregnant women is proposed. CONCLUSIONS: analysis of the literature shows that obesity is associated with an increased duration of pregnancy and prolonged duration of first stage of labour. IMPLICATIONS FOR PRACTICE: an adapted clinical approach is suggested in these patients.