In this cohort study, uterine contractions were recorded in 81 low-risk pregnant women who wore ambulatory tocodynamometers continuously during three 72-hour periods at advancing gestational ages. During these periods, they also recorded their daily activities in a diary. Examination of the data, in general, revealed no association between uterine contraction frequency and habits such as smoking, alcohol consumption, or drinking caffeinated beverages. Physical activities, such as prolonged standing, heavy housework, lifting, or organized exercise also did not appear to affect uterine contraction rates. Only climbing stairs and walking were associated with increased contraction frequencies, but this effect, although statistically significant, was relatively small in magnitude and was present only during the last gestational age period monitored (30 to 33 weeks).