Severe influenza during pregnancy: which trimester?
In this large series of pregnant and postpartum patients who were hospitalized with or died from 2009 H1N1 influenza, 95% of the pregnant patients were infected in the second or third trimester. The fact that eight of the cases of influenza in this study involved a postpartum onset of symptoms, with severe disease and death in some of these cases, highlights the continued high risk immediately after pregnancy.
Should pregnant women receive the H1N1 influenza vaccine?
Pregnant women are a top-priority group for immunization against 2009 H1N1 influenza. Since the 2009 H1N1 monovalent vaccine is manufactured according to the same processes that are used for the seasonal influenza vaccine, its safety profile among pregnant women is expected to be similar to that of the seasonal influenza vaccine, which has consistently been shown to be safe during pregnancy. Preliminary results from a trial of 2009 H1N1 monovalent vaccine have shown a robust immune response in pregnant women, similar to the response in nonpregnant adults, and no safety concerns have been identified. Maternal vaccination may also provide a benefit to the newborn infant, with a decreased risk of respiratory infections related to influenza in both the mother and infant during the first 6 months after delivery.
How should pregnant women with H1N1 influenza infection be treated?
Regardless of the results of rapid antigen tests, women with suspected or confirmed influenza who are pregnant or who have delivered within the previous 2 weeks should receive aggressive antiviral treatment and undergo close monitoring. The Centers for Disease Control and Prevention (CDC) recommends prompt antiviral treatment of pregnant women with suspected or confirmed 2009 H1N1 influenza, ideally within 48 hours after symptom onset.
What underlying condition most commonly predisposed pregnant women to complications from H1N1 influenza infection?
A total of 32 of the 93 pregnant women for whom data were available (34%), 2 of the 8 postpartum women (25%), and 82 of the 137 nonpregnant women (60%) had underlying conditions besides pregnancy that placed them at increased risk for complications from influenza; the most common condition was asthma, affecting 16% of pregnant women and 28% of nonpregnant women.