Is Metronidazole Safe in Pregnancy

Status

caution Last reviewed: 2026-05-16 · Confidence: moderate

Reason

Official labels say pregnancy use needs caution; first trimester use needs careful evaluation.

Drug Information

Brand Name
Flagyl
Generic Name
metronidazole
Drug Class
nitroimidazole antibiotic and antiprotozoal
FDA Category
B
Rx Status
prescription

Safe Amount

Dosage must be determined by your provider based on individual risk/benefit.

Effects

Pregnancy
Placental transfer occurs. Official labels note caution in pregnancy, especially in the first trimester.
Mother
Can treat infections that may also harm the mother if untreated. May cause side effects and can interact with alcohol and blood thinners.
Baby
Available data have not shown a clear link to major birth defects, miscarriage, or other adverse fetal outcomes. First-trimester use should be carefully evaluated.

Trimester Notes

1st Trimester
Careful evaluation is advised. Some older labels list first-trimester use as contraindicated for trichomoniasis; current labeling notes limited human data and placental transfer.
2nd Trimester
Generally used with caution when clearly needed. Official data have not established an association with major birth defects or miscarriage.
3rd Trimester
Official labeling says use should be restricted to cases where alternative treatment has been inadequate in some labels; current labels note no established link to major birth defects or other adverse outcomes.

Risk-Benefit Note

Treating infection during pregnancy may be important. Do not stop or switch the medicine without your prescriber’s advice.

Conditions & Warnings

  • Consult OB/GYN or prescriber
  • Prescription drug: review before starting, stopping, or continuing
  • Bacterial vaginosis
  • Trichomoniasis
  • Other anaerobic infections

Alternatives

  • Consult your OB/GYN or prescriber for infection-specific options
  • Topical metronidazole may be an option for some conditions if your prescriber recommends it

References

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