Impact on pregnancies in south Brazil from the influenza A (H1N1) pandemic: cohort study.

Introduction: The emergence of a new subtype of the influenza virus in 2009 generated interest in the international medical community, the media, and the general population. Pregnant women are considered to be a group at risk of serious complications related to the H1N1 influenza virus. The aim of this study was to evaluate the outcomes and teratogenic effects of pregnancies exposed to the H1N1 virus during the Influenza A epidemic that occurred in the state of Rio Grande do Sul in 2009.

Methods: This is an uncontrolled prospective cohort study of pregnant women with suspected symptoms of Influenza A who were reported in the Information System for Notifiable Diseases-Influenza (SINAN-Influenza) during the epidemic of 2009 (database from the state of Rio Grande do Sul, Brazil). There were 589 cases of pregnant women with suspected infection. Among these, 243 were tested by PCR and included in the analysis. The main outcome measures were: maternal deaths, pregnancy outcome, stillbirths, premature births, low birth weight, congenital malformations, and odds ratios for H1N1+ and non-H1N1 pregnant women.

Results: There were one hundred and sixty-three (67%) confirmed cases of H1N1, 34 cases (14%) of seasonal Influenza A and 46 (19%) who were negative for Influenza A. There was no difference between the three groups in clinical parameters of the disease. There were 24 maternal deaths--18 of them had H1N1. There were 8 stillbirths--5 were children of H1N1 infected mothers. There were no differences in perinatal outcomes.

Conclusions: The present data do not indicate an increase in teratogenic risk from exposure to the influenza A (H1N1) virus. These results will help to strengthen the data and clarify the health issues that arose after the pandemic.