Pregnancy outcome after gestational exposure to metronidazole: a prospective controlled cohort study.
BACKGROUND
Metronidazole is an important antibacterial agent commonly used in women of reproductive age. Its use in pregnancy is a reason for concern for women and their health care providers. The objective was to examine the fetal safety of metronidazole.


METHODS
The Israeli Teratogen Information Service prospectively collected and followed up 228 women exposed to metronidazole in pregnancy, 86.2% of whom with first-trimester exposure. Pregnancy outcome was compared with that of a control group, who were counseled during the same period for nonteratogenic exposure.


RESULTS
There was no difference in the rate of major malformations between the groups (3/190; 1.6% [metronidazole] vs. 8/575; 1.4% [control], P = 0.739). The rate of major malformations did not differ between the groups even after including elective terminations of pregnancy due to prenatally diagnosed malformations (5/192; 2.6% [metronidazole] vs. 12/579; 2.1% [control], P = 0.777). A reduced neonatal birth weight was found in the metronidazole group compared with controls without significant differences in the rate of prematurity or in gestational age at delivery. The mean birth weight was lower in the metronidazole group when comparing the subgroup of term infants.


CONCLUSIONS
This study confirms that metronidazole does not represent a major teratogenic risk in humans when used in the recommended doses.
Diav-Citrin
O
O
Israeli Teratogen Information Service, Israeli Ministry of Health, Jerusalem 91120, Israel.
Shechtman
S
S
Gotteiner
T
T
Arnon
J
J
Ornoy
A
A
D000014:Abnormalities, Drug-Induced / Q000453:epidemiology; D000328:Adult; D000890:Anti-Infective Agents / Q000009:adverse effects*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008795:Metronidazole / Q000009:adverse effects*; D011247:Pregnancy; D011256:Pregnancy Outcome; D011261:Pregnancy Trimester, First; D011446:Prospective Studies; D012307:Risk Factors; D013723:Teratogens
D000890:Anti-Infective Agents; D013723:Teratogens; D008795:Metronidazole