Metronidazole Use in Pregnancy

Rationale for Contraindication

• The Centers for Disease Control and Prevention recommends that metronidazole is contraindicated in the first trimester of pregnancy due to precautionary concerns, although evidence does not conclusively demonstrate teratogenicity in humans 1, 2, 3
• Historical concerns stemmed from animal studies using extremely high and prolonged doses that suggested possible mutagenicity, though this has not been demonstrated in humans 1, 4

Management Recommendations for Infections During Pregnancy

Bacterial Vaginosis

• For BV treatment during first trimester, clindamycin vaginal cream is the preferred alternative 1, 3, 4
• During second and third trimesters, oral metronidazole can be used safely 3, 4

Trichomoniasis

• For trichomoniasis, treatment should be delayed until after the first trimester 2, 5
• After first trimester, metronidazole 2g orally in a single dose is recommended 2, 5

Clinical Considerations

• When treating pregnant women with metronidazole after the first trimester, lower doses are recommended to minimize fetal exposure 6, 7
• For high-risk pregnant women with BV, treatment in the second trimester may help reduce risk of preterm delivery 6, 7