Is it safe to use Tamiflu (oseltamivir) at 35 weeks pregnant?

Can You Use Tamiflu at 35 Weeks Pregnant?

Yes, oseltamivir (Tamiflu) is safe and strongly recommended at 35 weeks of pregnancy for any pregnant woman with suspected or confirmed influenza, and treatment should begin immediately without waiting for laboratory confirmation. 1, 2

Treatment Recommendations

The American College of Obstetricians and Gynecologists (ACOG) and CDC explicitly recommend oseltamivir 75 mg orally twice daily for 5 days for pregnant women with suspected or confirmed influenza at any gestational age, including 35 weeks. 1, 2

• Treatment should start immediately upon suspicion of influenza, ideally within 48 hours of symptom onset, but should not be withheld even if this window is missed 1, 2
• The same adult dosing applies to pregnant women—no dose adjustment is needed 1
• Pregnancy is explicitly not a contraindication to oseltamivir use 1, 3
• Take with food to reduce nausea, which occurs in approximately 10% of patients 3

Why Aggressive Treatment Is Critical at 35 Weeks

Pregnant women at 35 weeks face the highest risk of severe influenza complications, with a 4.7-fold increased risk of hospitalization compared to non-pregnant women. 1

• The relative risk for hospitalization increases progressively throughout pregnancy, peaking at 37-42 weeks 1
• Influenza in late pregnancy increases risks of maternal death, stillbirth, preterm delivery, and low birth weight 1, 4
• Fever itself poses direct risks to fetal development, making prompt treatment essential 3

Safety Profile in Late Pregnancy

Extensive post-marketing surveillance of over 5,000 pregnant women exposed to oseltamivir, including more than 1,000 first-trimester exposures, shows no increased risk of birth defects, preterm delivery, or adverse fetal outcomes. 4, 5, 6

• No adverse effects have been reported among women who received oseltamivir during pregnancy or their infants 1, 3, 4
• A prospective cohort study of 716 pregnant women found no evidence of increased risks for major birth defects (RR 0.84,95% CI 0.19-2.80), preterm delivery (HR 0.65,95% CI 0.26-1.63), or small-for-gestational-age infants 5
• Post-marketing data from 2,128 exposed pregnancies showed spontaneous abortion rates of 2.9% and preterm delivery rates of 4.2%—both lower than background population rates 6

Alternative Treatment Option

• Zanamivir 10 mg (two 5 mg inhalations) twice daily for 5 days can be used if oseltamivir is contraindicated, though oseltamivir remains first-line 1
• Zanamivir has limited systemic absorption but carries potential respiratory complications in women with underlying respiratory conditions 1

Concurrent Fever Management

• Use acetaminophen for fever control, as fever itself can cause adverse fetal outcomes 3
• Treating influenza with oseltamivir may actually reduce fetal risk by shortening illness duration and reducing fever 3

Warning Signs Requiring Urgent Evaluation

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

Important Clinical Caveat

While the FDA classifies oseltamivir as Pregnancy Category C due to lack of controlled trials, this cautious language predates extensive post-marketing surveillance and the 2009 H1N1 pandemic experience, which demonstrated both the severe risks of untreated influenza in pregnancy and the reassuring safety profile of oseltamivir. 3, 4 The benefits of treatment far outweigh theoretical risks at 35 weeks gestation.