Terbinafine in Pregnancy: Safety and Recommendations
If you discover you're pregnant while taking terbinafine, you can safely continue the medication, though it's reasonable to discontinue it since fungal nail infections are not urgent and treatment can be postponed until after delivery.
Evidence-Based Assessment
FDA Classification and Safety Data
Terbinafine is classified as FDA Pregnancy Category B, meaning it is not expected to harm an unborn baby 1, 2. The FDA label explicitly states: "There are no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, and because treatment of onychomycosis can be postponed until after pregnancy is completed, it is recommended that terbinafine not be initiated during pregnancy" 2.
Animal studies at doses up to 12-23 times the maximum recommended human dose showed no evidence of impaired fertility or harm to the fetus 2.
Recent High-Quality Research Evidence
The most compelling evidence comes from a 2020 nationwide Danish registry study 3 examining 1,650,649 pregnancies over 20 years:
- No increased risk of major malformations: Prevalence odds ratio 1.01 (95% CI, 0.63-1.62) for oral terbinafine vs unexposed pregnancies
- Absolute risk difference of only 0.04% (95% CI, -1.69% to 1.76%)
- No increased risk of spontaneous abortion: Hazard ratio 1.06 (95% CI, 0.86-1.32)
- Similar safety profile for topical terbinafine
A 2022 systematic review 4 corroborated these findings, concluding that "the use of systemic and topical terbinafine during pregnancy can be regarded as safe for mothers and unborn children."
Clinical Decision Algorithm
If Already Pregnant and Taking Terbinafine:
- Assess the indication: Onychomycosis (nail fungus) is not life-threatening and poses no risk to the fetus
- Consider discontinuation: Since treatment can be safely postponed until after delivery without medical consequences 1
- If continuing treatment: The evidence supports safety, with no increased risk of malformations or miscarriage 3
- Discuss risks vs benefits: The decision should weigh the psychological impact of untreated infection against theoretical concerns
If Trying to Conceive:
You should ideally discontinue terbinafine before attempting conception 2. The rationale is:
- Treatment of onychomycosis is not urgent and can be postponed 1
- While evidence shows safety, the FDA recommendation is to avoid initiating during pregnancy
- Terbinafine has a long half-life (200-400 hours in tissues) 2, so stopping before conception allows clearance
Important Caveats
Breastfeeding Considerations
Terbinafine is NOT recommended during breastfeeding 2. The drug passes into breast milk at a 7:1 ratio (milk to plasma), which could affect a nursing baby 2.
Contrast with Azole Antifungals
Unlike terbinafine, azole antifungals (itraconazole, fluconazole) have documented teratogenic potential and should be strictly avoided in pregnancy 1, 5, 6. This makes terbinafine's safety profile relatively favorable among systemic antifungals.
Male Fertility Concerns
One case report 7 suggested terbinafine may affect sperm DNA fragmentation, though this requires further study. Men planning to father children may want to discuss timing with their physician, though griseofulvin (not terbinafine) is the antifungal with established warnings about male fertility 6.
Practical Recommendation
For a woman who discovers pregnancy while on terbinafine: Stop the medication and reassure her that exposure to date carries no demonstrated increased risk of harm based on the best available evidence 3. Complete the pregnancy without antifungal treatment and resume therapy postpartum if not breastfeeding. The nail infection will not worsen pregnancy outcomes or harm the baby 1.