Uterine contractions preceding labor

OBJECTIVE: To evaluate whether 12 contractions in 1 hour is a meaningful signal that spontaneous labor has begun or is imminent. METHODS: This prospective observational cohort study includes all women reporting contractions who presented to a labor and delivery triage unit between August 1 and October 31, 2006, who met the following criteria: 1) 36 0/7 to 41 6/7 weeks of gestation, 2) cervical dilation less than 4 cm, 3) intact membranes, and 4) no other medical or obstetric complications that might influence admission. Each woman received external fetal monitoring for a minimum of 1 hour. Women were discharged home if cervical dilation did not advance and the fetal heart rate pattern was reassuring. Women who progressed to a cervical dilation of 4 cm were admitted with the diagnosis of labor. RESULTS: Among 768 women studied, labor was diagnosed within 24 hours in 268 (76%) with 12 or more contractions per hour compared with 216 (52%) of 416 women with fewer than 12 contractions per hour, P<.001. Cervical condition and fetal station were more advanced on presentation in women with 12 or more contractions per hour. CONCLUSION: Twelve contractions or more per hour at term is a meaningful signal that true labor has either begun or is imminent. LEVEL OF EVIDENCE: II.