What is the recommended treatment for a pregnant woman diagnosed with influenza?

Treatment for Influenza in Pregnancy

All pregnant women with suspected or confirmed influenza should receive oseltamivir 75 mg orally twice daily for 5 days, starting immediately without waiting for laboratory confirmation, regardless of trimester, vaccination status, or timing of symptom onset. 1, 2, 3

First-Line Antiviral Treatment

• Oseltamivir is the preferred antiviral agent for pregnant women with influenza, with standard adult dosing of 75 mg orally twice daily for 5 days 1, 2, 4, 3
• Treatment should begin as soon as possible after symptom onset, ideally within 48 hours, but should not be withheld even if this window is missed 1, 3
• Pregnancy is explicitly not a contraindication to oseltamivir use—the same dosing regimen used in non-pregnant adults applies 1
• Treatment can be initiated over the phone for low-risk patients to reduce disease spread in clinical settings 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 5, 1, 2
• Zanamivir has limited systemic absorption but carries potential respiratory complications, particularly in women with underlying respiratory conditions 1
• Zanamivir is generally not recommended for patients with underlying airway disease due to risk of serious adverse events 5

Clinical Rationale for Aggressive Treatment

The evidence overwhelmingly supports immediate antiviral treatment due to severe maternal and fetal risks:

• Pregnant women face disproportionately high death rates during influenza pandemics and are 7.2% more likely to be hospitalized than non-pregnant women 5, 2
• The relative risk for hospitalization escalates dramatically from 1.4 at weeks 14-20 of gestation to 4.7 at weeks 37-42 compared to postpartum women 1, 2
• Pregnant women are at higher risk for severe illness, pneumonia, ICU admission, and death compared to non-pregnant women 1, 2
• 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, 2

Safety Profile of Oseltamivir in Pregnancy

The safety data strongly supports oseltamivir use throughout pregnancy:

• No adverse effects have been reported among women who received oseltamivir during pregnancy or among infants born to such women 1
• Studies of over 2,000 pregnant women demonstrated no adverse fetal effects from oseltamivir 2
• The FDA classifies oseltamivir as Pregnancy Category C, but extensive post-marketing surveillance and observational data demonstrate reassuring safety outcomes 1
• Animal and toxicology studies do not suggest that clinically effective dosages have potential to produce adverse effects on fetal development 6
• Transplacental transfer of oseltamivir and its active metabolite is very limited and not detectable at normal therapeutic doses 6

The critical principle: inadequately controlled influenza poses a greater risk to the fetus than oseltamivir treatment—maternal hypoxia from severe symptoms is more dangerous than appropriate medication use 7

Managing Common Side Effects

• Taking oseltamivir with food significantly reduces nausea and vomiting, which occur in approximately 10% and 9% of patients respectively 1, 2
• Only 1% of patients discontinue treatment due to gastrointestinal side effects 1
• Acetaminophen should be used concurrently for fever management, as fever itself poses risks to fetal development 1

Post-Exposure Prophylaxis

• For pregnant women exposed to influenza, oseltamivir 75 mg once daily for 7-10 days after last exposure is recommended for high-risk and moderate-risk exposure 1, 2
• Prophylaxis should be initiated within 48 hours following close contact with an infected individual 4
• The CDC advises that postexposure antiviral chemoprophylaxis can be considered for pregnant women and women up to 2 weeks postpartum (including after pregnancy loss) who have had close contact with infectious individuals 3

Warning Signs Requiring Urgent Evaluation

Monitor for these complications that require immediate assessment:

• Difficulty breathing or chest pain 1, 2
• Persistent high fever despite acetaminophen 1, 2
• Decreased fetal movement 1, 2
• Signs of preterm labor 1, 2

Important Caveats

• Do not delay treatment waiting for laboratory confirmation—treat presumptively based on clinical evaluation 1, 3
• Pregnancy-related physiologic changes may alter oseltamivir pharmacokinetics, resulting in lower exposure to the active metabolite in pregnant women, but this predicted exposure is still expected to have activity against susceptible influenza virus strains 4
• No dose adjustment is recommended for pregnant women despite these pharmacokinetic differences 4
• Live attenuated influenza vaccine (LAIV, intranasal) is contraindicated during pregnancy, but inactivated influenza vaccine should be administered during any trimester for future protection 5, 2