Post-pandemic influenza A (H1N1) 2009 virus infection in pregnant women in Ceará, Brazil

OBJECTIVE: The aim of this study was to present results of the post-pandemic phase of A(H1N1)pdm09 virus infection in pregnant women in Ceará, Brazil, during the January–June 2012 influenza season. RESULTS: One hundred and fifty-four nasopharyngeal swab samples were collected from pregnant women admitted to hospitals with suspected severe acute respiratory infection (SARI). Fifty-three (34·4%) had laboratory-confirmed A(H1N1)pdm09 virus infection with 15 (28·3%) outpatients and 38 (71·7%) hospitalized. Five (9·4%) women were in the first trimester of pregnancy, 20 (37·7%) in the second trimester of pregnancy, and 24 (45·2%) in the third trimester of pregnancy. Three had no information about the time of pregnancy. Six samples from newborns were also analyzed, of which three were nasopharyngeal swab positive for A(H1N1)pdm09. These swabs were collected immediately after birth, with the exception of one that was collected on the day after birth. CONCLUSION: Our findings suggest that transplacental transfer of influenza viruses could occur as a result of severe illness in pregnancy. It is therefore important to encourage women to be vaccinated against influenza in order to avoid pregnancy complications.