Antivirals in Pregnancy
FOR USE BY MEDICAL PROFESSIONALS.
The prescribing clinician must review full product labeling and current CDC/ACIP/NIH guidance.
Adjust doses for renal impairment when applicable and consider drug–drug interactions (notably ritonavir-boosted regimens).
Quick index
Clinical pearls
- HSV suppression Many protocols use suppressive acyclovir/valacyclovir starting at 36 weeks for recurrent genital HSV to reduce lesions/viral shedding at delivery (see CDC STI guidance).
- Influenza in pregnancy Treat suspected/confirmed influenza promptly (do not wait for testing if high suspicion); oseltamivir is commonly preferred.
- COVID-19 For eligible outpatients at risk for progression, ritonavir-boosted nirmatrelvir is widely used; check interactions and renal function.
- HBV For HBsAg+ patients with high HBV DNA, third-trimester antiviral prophylaxis plus newborn vaccine + HBIG reduces perinatal transmission risk.
HSV / Varicella-Zoster (VZV)
Acyclovir
Commonly used HSV (genital/orolabial), VZV (varicella/zoster). Renal dose adjustment required.
How administered
Oral; IV for severe/disseminated disease.
Typical adult dosing (examples)
- Herpes zoster: 800 mg PO 5 times daily (about q4h while awake) for 7–10 days.
- First episode genital HSV: 200 mg PO 5 times daily for 10 days (alternative regimens exist by guideline).
- Suppressive therapy (recurrent genital HSV): 400 mg PO twice daily (reassess periodically).
- Severe/disseminated HSV (e.g., pneumonitis, hepatitis, CNS): 5–10 mg/kg IV q8h, then step down to oral to complete ≥10 days total therapy (use guideline-based approach).
- Varicella (adults): 800 mg PO 4 times daily for 5 days (start early).
How supplied
Tablets/capsules, oral suspension, and IV formulation (product-specific presentations; see label).
Label / package insert
Pregnancy / lactation
Generally considered compatible when indicated (large experience base). Consider suppressive therapy near term for recurrent genital HSV per guideline/protocol.
Breastfeeding: refer to LactMed/labeling.
Valacyclovir
Commonly used Prodrug of acyclovir with convenient dosing. Renal dose adjustment required.
How administered
Oral.
Typical adult dosing (examples)
- Herpes zoster: 1 g PO three times daily for 7 days (start ASAP).
- First episode genital HSV: 1 g PO twice daily for 10 days (start within 48 hours if possible).
- Recurrent genital HSV episodes: 500 mg PO twice daily for 3 days (start within 24 hours of symptoms/lesions).
- Suppressive therapy (recurrent genital HSV): 500 mg PO daily (selected patients) or 1 g PO daily (common). Many obstetric protocols use suppression beginning at 36 weeks.
How supplied
Caplets/tablets in multiple strengths; see label.
Label / package insert
Pregnancy / lactation
Widely used when indicated. Consider suppressive therapy near term for recurrent genital HSV per guideline/protocol.
Famciclovir
Alternative Used for HSV/VZV; pregnancy experience is more limited than acyclovir/valacyclovir.
How administered
Oral.
Typical adult dosing (examples)
- Herpes zoster: 500 mg PO every 8 hours for 7 days (start early; decreased benefit if started late after rash onset).
- Recurrent genital HSV: 125 mg PO twice daily for 5 days (start early after symptom onset).
- Suppressive therapy (recurrent genital HSV): 250 mg PO twice daily (reassess periodically).
How supplied
Tablets in multiple strengths; see label.
Label / package insert
Pregnancy / lactation
Consider acyclovir/valacyclovir first-line in pregnancy when appropriate; use famciclovir when clinically indicated and alternatives are not suitable.
Influenza antivirals
Oseltamivir (Tamiflu)
Preferred in pregnancy (commonly) Neuraminidase inhibitor for treatment and prophylaxis.
How administered
Oral (capsules; oral suspension available).
Typical adult dosing
- Treatment: 75 mg PO twice daily for 5 days.
- Post-exposure prophylaxis: 75 mg PO once daily for 7–10 days (protocol-dependent; align with CDC/ACIP/local policy).
How supplied
Capsules (multiple strengths) and oral suspension (see label).
Label / package insert
Pregnancy / lactation
Treat promptly in pregnancy when influenza is suspected/confirmed (benefit greatest when started early, but treat even if later in course when clinically indicated).
Zanamivir (Relenza)
Alternative Inhaled neuraminidase inhibitor; avoid in patients with reactive airway disease unless benefits outweigh risks.
How administered
Oral inhalation (Diskhaler device).
Typical adult dosing
- Treatment: Two 5-mg inhalations (10 mg total) twice daily for 5 days.
- Post-exposure prophylaxis: Two 5-mg inhalations (10 mg total) once daily for 7–10 days (protocol-dependent).
How supplied
Rotadisks (blister packs) used with Diskhaler inhalation device; see label.
Label / package insert
Pregnancy / lactation
May be used when clinically appropriate; consider asthma/COPD risk with inhaled route.
Peramivir (Rapivab) — IV
IV option For selected patients who cannot take oral/inhaled therapy or are severely ill (follow CDC/ID/OB protocol).
How administered
Intravenous infusion.
Typical adult dosing
- Treatment (uncomplicated influenza, adults): commonly 600 mg IV single dose infused over ~15–30 minutes (label/clinical protocol dependent).
How supplied
Injection solution/vials (see label).
Label / package insert
Pregnancy / lactation
May be considered when clinically indicated; align with CDC guidance and institutional protocols.
Baloxavir marboxil (Xofluza)
Not recommended routinely in pregnancy Limited pregnancy data; CDC guidance generally advises against use in pregnancy and breastfeeding.
How administered
Oral (single-dose regimen based on body weight; see label).
How supplied
Tablets and oral suspension formulations (see label).
Label / package insert
Pregnancy / lactation
Avoid Prefer oseltamivir (or zanamivir/peramivir when appropriate) in pregnancy unless expert-guided exception.
COVID-19 antivirals / therapeutics
Nirmatrelvir/ritonavir (Paxlovid)
Common outpatient option For eligible patients at risk for progression. Check renal function and drug–drug interactions.
How administered
Oral (two drugs taken together for a 5-day course; see labeling for exact regimen and renal adjustments).
How supplied
Co-packaged tablets (dose pack); see label for strengths and renal-dose packaging.
Label / package insert
Pregnancy / lactation
Consider when clinically indicated for pregnant patients who meet eligibility criteria. Review interactions carefully (CYP3A inhibition from ritonavir) and follow current NIH/OB guidance.
Remdesivir (Veklury) — IV
IV option Used for selected patients (inpatient and certain outpatient protocols). Monitor hepatic function per label/protocol.
How administered
Intravenous infusion (multi-day regimen; see label and current NIH guidance).
How supplied
IV formulation (vials/powder/solution depending on product); see label.
Label / package insert
Pregnancy / lactation
Used when clinically indicated; follow NIH/OB protocols and weigh maternal benefit versus potential risks per labeling.
Hepatitis B antivirals (HBV)
Antiviral prophylaxis in late pregnancy is commonly used for HBsAg-positive patients with high HBV DNA to reduce perinatal transmission, in addition to newborn hepatitis B vaccine + HBIG at birth (per guideline/protocol).
Tenofovir disoproxil fumarate (Tenofovir DF, TDF) — HBV
Preferred (commonly) Nucleotide reverse transcriptase inhibitor used for chronic hepatitis B; widely used in pregnancy when indicated.
How administered
Oral.
Typical adult dosing (HBV)
- Chronic HBV (typical): 300 mg PO once daily.
- Pregnancy (per common protocols): start in the third trimester (often ~28–32 weeks) for patients with high HBV DNA (≥ 200,000 IU/mL, 5.3 log 10); continue through delivery and consider continuing for a limited postpartum period with monitoring for hepatic flare per hepatology/OB guidance.
How supplied
Tablets (multiple strengths depending on product) and oral powder formulations may be available; see the specific product label.
Manufacturer label link
VIREAD (tenofovir disoproxil fumarate) — official site (Prescribing Information)
Note: Many HBV patients will be treated with generic tenofovir DF; always confirm the exact product/strength and current labeling.
Pregnancy / lactation
Used in pregnancy when indicated for maternal HBV management and/or to reduce perinatal transmission risk as part of the prevention bundle.
Breastfeeding considerations vary by clinical context—consult labeling and specialist guidance.
Standard OBPharm/OBRx disclaimer
THE INFORMATION IN THE OBPHARM/OBRx CONTENT IS INTENDED SOLELY FOR USE BY THE MEDICAL PROFESSION. IT IS NOT INTENDED FOR LAY PERSONS.
The prescribing physician must be familiar with full product labeling and relevant medical literature prior to use.
UPDATED: 12/18/2025
References (guidelines + key resources)
- CDC STI Treatment Guidelines (Herpes simplex; pregnancy considerations; suppressive therapy near term): CDC link
- CDC Influenza Antiviral Medications — Summary for Clinicians (pregnancy considerations; preferred agents): CDC link
- ACOG — Influenza in Pregnancy: Prevention and Treatment (updated guidance): ACOG link
- NIH COVID-19 Treatment Guidelines (pregnancy/lactation considerations; outpatient and inpatient therapies): NIH link
- Tenofovir DF (HBV) — Manufacturer labeling: VIREAD official site
- ML Badell, M Prabhu, J Dionne, ATN Tita, NS Silverman, SMFM Publications Committee Society for Maternal-Fetal Medicine Consult Series #69: Hepatitis B in pregnancy: updated guidelines SMFM, 2024 SMFM link
- DailyMed (labeling search): DailyMed home
Note: Dosing examples above are common adult regimens and may vary by indication, severity, renal function, resistance patterns, and evolving guidance. Always verify against current label/guidelines and local protocols.