What can be done to decrease their risk?
The first step is preventing infection. For the 2009-2010 season, vaccination against seasonal and 2009 H1N1 influenza is strongly recommended for all pregnant women. Only the intramuscular injection is approved for pregnant women. Patients can receive the seasonal influenza vaccine at the same time as the H1N1 vaccine using an alternate injection site.
Maternal immunization against seasonal influenza benefits mothers and has also been shown to lower infection rates in infants. A study published in The New England Journal of Medicine showed that the seasonal influenza vaccination given to pregnant women reduced influenza-like illness in their infants younger than 6 months of age by 63%.9 Also important is providing chemoprophylaxis for pregnant women who have close contacts with suspected or confirmed influenza infection. For 2009 H1N1 chemoprophylaxis, a 10-day course of once-daily oseltamivir or zanamivir is acceptable. Zanamivir is an inhaled medication and should not be prescribed to patients with asthma or other respiratory conditions.
Confirmed case? Tx for the pregnant patient
The 2009 H1N1 virus is susceptible to oseltamivir and zanamivir.1 Both antivirals are Category C in pregnancy. The CDC recommends that patients with suspected or confirmed 2009 H1N1 infection who are in high-risk groups (which includes pregnant women) be treated with oseltamivir.
Antiviral medications such as oseltamivir and zanamivir act at the viral replication stage, which peaks at 24 to 72 hours in influenza.10 This helps explain evidence that the earlier treatment of influenza is initiated—within the first 48 hours—the more effective it is in reducing fever, relieving symptoms, and decreasing time to return to baseline activity.11 A study of pregnant women in California with severe 2009 H1N1 infection found that later treatment (>2 days after symptom onset) was associated with 4 times the risk of admission and death.3 For these reasons, treatment should not be delayed while test results are pending.
That said, in hospitalized patients with seasonal influenza, initiating treatment after 48 hours of symptom onset has been shown to provide some benefit in some observational studies.1,12 Consequently, the CDC recommends initiating treatment of high-risk patients who seek care more than 48 hours after symptom onset.1
The standard course of oseltamivir is 75 mg twice daily for 5 days. Longer courses may be beneficial in hospitalized patients.1 Oseltamivir and zanamivir can also be continued while breastfeeding.13
Our patient’s outcome
The patient received a 10-day course of oseltamivir (rather than the standard 5-day course), as well as empiric broad-spectrum antibiotic coverage for community-acquired pneumonia and aspiration pneumonia, including coverage for Streptococcus pneumoniae (the most common bacterial cause of secondary pneumonia in influenza14).
The cultures come back. Nasopharyngeal cultures were negative × 2 for type A influenza. Blood cultures were negative throughout the admission. Sputum cultures were negative, as well. Bronchoscopy cultures, however, were positive for type A influenza and negative for bacterial and fungal pathogens, confirming a diagnosis of primary pneumonia from 2009 H1N1 infection.
The patient was extubated 1 week after her arrival at our hospital and continued to recover during the rest of her hospital stay. She was discharged in stable condition. Several weeks later, she delivered a full-term infant with average weight and normal Apgar scores.
CORRESPONDENCE: Christopher Bernheisel, MD, Director, Family Medicine Inpatient Service, The University of Cincinnati, 2123 Auburn Ave., Suite 340, Cincinnati, OH 45219; bernheiseljfp@me.com