Maintenance nifedipine tocolysis compared with placebo: a randomized controlled trial.
OBJECTIVE
To estimate whether maintenance nifedipine tocolysis after arrested preterm labor prolongs pregnancy and improves neonatal outcomes.


METHODS
A prospective, randomized double-blind, multicenter study was conducted. After successful tocolysis, patients were randomly assigned to receive 20 mg nifedipine or an identical-appearing placebo every 4-6 hours until 37 weeks of gestation. The primary outcome was attainment of 37 weeks of gestation. Patients were enrolled between 24 weeks and 34 weeks if they had six or fewer contractions per hour, intact membranes, and less than 4 cm cervical dilation. Exclusion criteria were placental abruption or previa, fetal anomaly incompatible with life, or maternal medical contraindication to tocolysis. Sixty-six patients were required for 80% power to detect a 50% reduction in birth before 37 weeks, with a two-tailed alpha of 0.05. Data were analyzed by intent to treat.


RESULTS
Seventy-one patients were randomly assigned. Two patients were excluded after randomization and one was lost to follow-up. Thirty-five patients received placebo, and 33 received nifedipine. There were no maternal demographic differences between groups; the placebo group was significantly more dilated and effaced at study entry. There was no difference in attainment of 37 weeks (39% nifedipine compared with 37% placebo, P>.91), mean delay of delivery (33.5+/-19.9 days nifedipine compared with 32.6+/-21.4 days placebo, P=.81) or delay of delivery for greater than 48 hours or 1, 2, 3, or 4 weeks. Neonatal outcomes were similar between groups.


CONCLUSIONS
When compared with placebo, maintenance nifedipine tocolysis did not confer a large reduction in preterm birth or improvement in neonatal outcomes.


BACKGROUND
ClinicalTrials.gov, www.clinicaltrials.gov, NCT00185952


METHODS
I.
Lyell
Deirdre J
DJ
From the Departments of Obstetrics and Gynecology, Lucile S. Packard Children's Hospital at Stanford University, Stanford, California; Santa Clara Valley Medical Center, Santa Clara, California; and University of California San Francisco, San Francisco, California.
Pullen
Kristin M
KM
Mannan
Jana
J
Chitkara
Usha
U
Druzin
Maurice L
ML
Caughey
Aaron B
AB
El-Sayed
Yasser Y
YY
D000328:Adult; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D009543:Nifedipine / Q000008:administration & dosage*; D007752:Obstetric Labor, Premature / Q000188:drug therapy*; D016017:Odds Ratio; D011247:Pregnancy; D047928:Premature Birth / Q000517:prevention & control*; D015149:Tocolytic Agents / Q000008:administration & dosage*; D016896:Treatment Outcome; D055815:Young Adult
D015149:Tocolytic Agents; D009543:Nifedipine