Awaiting cervical change for the diagnosis of preterm labor does not compromise the efficacy of ritodrine tocolysis.

We retrospectively studied 209 patients treated with ritodrine hydrochloride to determine whether change in cervical effacement or dilatation during a period of observation before therapy would result in decreased efficacy of ritodrine, as measured by delivery delays of 48 hours, 1 week, or until greater than or equal to 37 weeks' gestation; neonatal intensive care unit admission; and neonatal respiratory distress syndrome. Patients who were greater than or equal to 3 cm dilated on admission were at high risk of therapy failure by all outcome measures compared with patients less than 3 cm dilated. For patients less than 3 cm dilated on admission, there was no difference in outcome when patients treated for contractions only were compared with those treated after change in effacement or dilatation had been documented. We conclude that awaiting change in cervical effacement or dilatation to be more certain of the diagnosis of preterm labor will not compromise the efficacy of ritodrine tocolysis.