What are the approved medications for treating influenza in a pregnant female?

Approved Medications for Influenza in Pregnant Women

Oseltamivir 75 mg orally twice daily for 5 days is the first-line approved antiviral treatment for pregnant women with suspected or confirmed influenza, and should be initiated immediately regardless of trimester, vaccination status, or whether diagnostic testing has been performed. 1

First-Line Treatment

• Oseltamivir (Tamiflu) 75 mg orally twice daily for 5 days is the primary recommended antiviral agent for all pregnant women with suspected or confirmed influenza A or B 1, 2
• Treatment should begin immediately upon suspicion of influenza, without waiting for diagnostic test confirmation 1
• The American College of Obstetricians and Gynecologists recommends this treatment regardless of trimester or vaccination status 1
• Oseltamivir reduces risk of severe complications, ICU admission, maternal death, and adverse fetal outcomes when started within 48 hours of symptom onset 1, 3

Alternative Treatment Option

• Zanamivir 10 mg (two 5 mg inhalations) twice daily for 5 days can be used if oseltamivir is contraindicated or unavailable 1
• Zanamivir is also approved for use during pregnancy and applies to pregnant women in high-risk and moderate-risk exposure groups 4

Safety Profile in Pregnancy

• Both oseltamivir and zanamivir are FDA Pregnancy Category C, meaning no controlled clinical trials have been conducted in pregnant women 4
• However, no adverse effects have been reported among women who received oseltamivir during pregnancy or among infants born to such women 4, 2
• The CDC explicitly states that "pregnancy should not be considered a contraindication to oseltamivir use" 2
• One retrospective cohort study found no association between oseltamivir use during pregnancy and preterm birth, premature rupture of membranes, malformations, or abnormal fetal weight 2
• Review of 115 pregnancy exposures showed spontaneous abortion rate of 6.1%, therapeutic abortion rate of 11.3%, and preterm delivery rate of 2.1%—all within normal background rates 5

Prophylaxis Dosing

• Oseltamivir 75 mg once daily for post-exposure prophylaxis in pregnant women with high-risk or moderate-risk exposure 4, 2
• Prophylaxis should continue for 7-10 days after last known exposure 4
• Pregnant women in low-risk exposure groups should not receive oseltamivir for chemoprophylaxis 4

Critical Clinical Considerations

Pregnant women are at substantially higher risk from influenza than non-pregnant women:

• Relative risk for hospitalization increases from 1.4 at weeks 14-20 of gestation to 4.7 at weeks 37-42 1
• Influenza infection during pregnancy is associated with increased odds of congenital anomalies, stillbirth, late pregnancy loss, preterm delivery, low birth weight, and small-for-gestational-age infants 1, 6
• Higher rates of ICU admission and maternal death occur in pregnant women with influenza 3

Adjunctive Management

• Acetaminophen should be used for fever management, as fever itself can cause adverse fetal outcomes 2
• Taking oseltamivir with food may reduce gastrointestinal side effects (nausea occurs in ~10% of patients, vomiting in ~9%) 2, 4

Important Caveats

• The benefit of treatment far outweighs theoretical risks, particularly given the severe consequences of untreated influenza in pregnancy 1, 3
• Treatment effectiveness is highest when initiated within 48 hours of symptom onset, but should still be given even if presenting later 1
• Urgent evaluation is required for: difficulty breathing, chest pain, persistent high fever, decreased fetal movement, or signs of preterm labor 1
• Live attenuated influenza vaccine (LAIV) is contraindicated during pregnancy; only inactivated influenza vaccine (IIV) should be used 1