Can I prescribe metronidazole (metro) gel to a pregnant patient?

Metronidazole Gel in Pregnancy

Do not prescribe metronidazole gel during the first trimester of pregnancy; use clindamycin vaginal cream 2% instead. After the first trimester, metronidazole gel can be used, though oral metronidazole is generally preferred for systemic coverage. 1, 2

First Trimester (Weeks 1-13)

Metronidazole gel is contraindicated in the first trimester. 3, 2 The CDC explicitly recommends against topical metronidazole agents during the first trimester, despite meta-analyses showing no conclusive evidence of teratogenicity in humans. 1, 2

Recommended Alternative:

• Clindamycin vaginal cream 2% is the first-line treatment: one full applicator (5g) intravaginally at bedtime for 7 days. 1
• This minimizes systemic fetal exposure while effectively treating bacterial vaginosis. 1

Critical Pitfall:

• Do not confuse clindamycin vaginal cream with clindamycin vaginal ovules—the ovules are not recommended during pregnancy. 1
• Clindamycin cream is oil-based and may weaken latex condoms and diaphragms. 1

Second and Third Trimesters (Week 14 onwards)

Metronidazole gel 0.75% can be used intravaginally after the first trimester, though oral metronidazole is generally preferred for better systemic coverage of potential upper genital tract infections. 1

Treatment Options:

• Oral metronidazole 250 mg three times daily for 7 days is the preferred systemic therapy. 1
• Metronidazole gel 0.75% intravaginally is an acceptable alternative regimen. 1
• Alternative: Metronidazole 2g orally as a single dose. 1

Evidence Supporting Safety:

• Meta-analyses show no association between metronidazole exposure in later trimesters and preterm birth, low birth weight, or congenital anomalies. 1
• The FDA classifies metronidazole as pregnancy category B (no evidence of harm in animal studies, but adequate human studies lacking). 1

Clinical Rationale for Treatment

Bacterial vaginosis in pregnancy is associated with serious adverse outcomes including premature rupture of membranes, preterm labor, preterm birth, postpartum endometritis, and post-cesarean wound infection. 1 All symptomatic pregnant women should be tested and treated. 1

Systemic vs. Topical Therapy:

• Systemic therapy (oral metronidazole) is generally preferred over topical therapy to treat possible subclinical upper genital tract infections, particularly in women at high risk for preterm delivery. 1
• However, research shows that both oral and vaginal metronidazole result in significant decreases in most BV-associated anaerobic bacteria, with only minor differences in bacterial eradication. 4
• Vaginal metronidazole may be less effective against certain fastidious bacteria like Leptotrichia, Sneathia, and BVAB1. 4

Follow-Up Considerations

• Follow-up visits are generally unnecessary if symptoms resolve. 1
• For high-risk pregnant women, consider a follow-up evaluation one month after treatment completion to ensure successful treatment. 1
• Treatment of male sex partners is not recommended as it does not influence treatment response or reduce recurrence rates. 1

Special Note on Trichomoniasis

If the patient has trichomoniasis (not bacterial vaginosis), metronidazole gel has not been studied for this indication and earlier topical preparations showed low efficacy. 3 For trichomoniasis in pregnancy, treatment should be delayed until after the first trimester, then oral metronidazole 2g as a single dose is recommended. 2