We examined background information and course of labour from a cohort of 2,810 low-risk nulliparas to identify possible lifestyle and anthropometrical risk indicators for dystocia. Criteria for dystocia: cervical dilatation <2 cm over 4 h during labour's active phase, or no descent during 2 h (3 h with epidural) in the descending phase, or no progress for 1 h during the expulsive phase. After adjustments, athletics or heavy gardening > or =4 h per week appeared protective for dystocia (OR 0.63, CI 0.45-0.89), contrary to a non-significant finding of intensive physical training (OR 1.57, CI 0.84-2.93). Caffeine intake of 200-299 mg/day was associated with dystocia (OR 1.37, CI 1.04-1.80); also high maternal age (OR 2.25, CI 1.58-3.22), small stature (OR 2.18, CI 1.51-3.15) and pre-pregnancy overweight (OR 1.28, CI 1.02-1.61). No association was found between dystocia and alcohol intake, smoking, night sleep and options for resting during the day.