Latent labor with an unknown uterine scar.

OBJECTIVE: To determine if avoiding the augmentation of ineffective contractions in women with unknown uterine scars would decrease the risk of cesarean for protraction disorders, compared with awaiting the onset of spontaneous labor.

METHODS: Term gravidas with one or two unknown uterine scars in early labor were randomized to nonintervention (N = 101) and intervention (N = 96) groups. Nonintervention subjects were discharged if cervical change did not occur within 4 hours. Intervention subjects were admitted. Contractions that persisted for 4 hours without cervical change were augmented with oxytocin.

RESULTS: Intervention subjects received oxytocin significantly more often (82 versus 55%, P < .001) and had a statistically significantly higher rate of uterine scar separation (5 versus 0%, P = .03). There was no difference between the two groups in length of active labor (4.0 versus 4.25 hours) or incidence of cesarean delivery (16 versus 17%).

CONCLUSION: The augmentation of ineffective contractions during latent labor in gravidas with an unknown uterine scar does not increase the rate of cesarean delivery, but it is significantly more likely to result in uterine scar separations.