Randomized clinical trial of metronidazole plus erythromycin to prevent spontaneous preterm delivery in fetal fibronectin-positive women.
OBJECTIVE
To estimate whether antibiotic treatment of asymptomatic women with a positive cervical or vaginal fetal fibronectin test in the second trimester would reduce the risk of spontaneous preterm delivery.


METHODS
Women were screened between 21 weeks 0 days and 25 weeks 6 days of gestation with cervical or vaginal swabs for fetal fibronectin. Women with a positive test (50 ng/mL or more) were randomized to receive metronidazole (250 mg orally three times per day) and erythromycin (250 mg orally four times per day) or identical placebo pills for 10 days. The primary outcome was spontaneous delivery before 37 weeks' gestation after preterm labor or premature membrane rupture.


RESULTS
A total of 16,317 women were screened for fetal fibronectin, and 6.6% had a positive test; 715 fetal fibronectin test-positive women consented to randomization. Outcome data were available for 703 women: 347 in the antibiotic group and 356 in the placebo group. The antibiotic and placebo groups were not significantly different for maternal age (P =.051), ethnicity (P =.849), marital status (P =.127), education (P =.244), and bacterial vaginosis (P =.236). No difference was observed in spontaneous preterm birth before 37 weeks' (odds ratio [OR] 1.17, 95% confidence interval [CI] 0.80, 1.70), less than 35 weeks' (OR 0.92, 95% CI 0.54, 1.56), or less than 32 weeks' (OR 1.94, 95% CI 0.83, 4.52) gestation in antibiotic- compared with placebo-treated women. Among women with a prior spontaneous preterm delivery, the rate of repeat spontaneous preterm delivery at less than 37 weeks' gestation was significantly higher in the active drug compared with the placebo group (46.7% versus 23.9%, P =.039).


CONCLUSIONS
Treatment with metronidazole plus erythromycin of asymptomatic women with a positive cervical or vaginal fetal fibronectin test in the late second trimester does not decrease the incidence of spontaneous preterm delivery.
Department of Obstetrics and Gynecology, Center for Research in Women's Health, University of Alabama at Birmingham, Birmingham, Alabama 35249-7333, USA. wandrews@uab.edu
William W
WW
Andrews
Baha M
BM
Sibai
Elizabeth A
EA
Thom
Donald
D
Dudley
J M
JM
Ernest
Donald
D
McNellis
Kenneth J
KJ
Leveno
Ronald
R
Wapner
Atef
A
Moawad
Mary J
MJ
O'Sullivan
Steve N
SN
Caritis
Jay D
JD
Iams
Oded
O
Langer
Menachem
M
Miodovnik
Mitchell
M
Dombrowski
D000328:Adult; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D000890:Anti-Infective Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D004359:Drug Therapy, Combination; D004797:Enzyme-Linked Immunosorbent Assay; D004917:Erythromycin / Q000008:administration & dosage / Q000627:therapeutic use*; D005260:Female; D005353:Fibronectins / Q000032:analysis*; D006801:Humans; D008795:Metronidazole / Q000008:administration & dosage / Q000627:therapeutic use*; D007752:Obstetric Labor, Premature / Q000517:prevention & control*; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D012307:Risk Factors
D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents; D005353:Fibronectins; D008795:Metronidazole; D004917:Erythromycin