Impact of influenza on outpatient visits and hospitalizations among pregnant women in Catalonia, Spain.

OBJECTIVE: To estimate outpatient visits and hospitalization rates due to cardiopulmonary illness attributable to influenza from 2008-09 to 2012-13 in a large cohort of pregnant women from Catalonia, Spain.

METHODS: We estimated the event rates occurring during influenza epidemic, influenza non-epidemic and non-influenza seasons, and by pregnancy status (one year before pregnancy, first, second and third trimester). We fitted quasi-Poisson models in order to identify the variables associated to higher event rates.

RESULTS: During influenza epidemic seasons, pregnant women in their second trimester had the highest rates of outpatient visits (153 per 10,000 women-months). An increased risk of outpatient visits was associated to first or second trimester (adjusted rate ratio (aRR) = 1.17; 95% CI, 1.10-1.23 and aRR, 1.36; 95% CI, 1.28-1.43, respectively) and having any comorbidity (aRR = 1.28; 95% CI, 1.21-1.36). Women during third trimester had the highest rates of hospitalizations (1.60 per 10,000 women-months), and an increased risk of hospitalization was significantly associated to third trimester (aRR, 1.85; 95% CI, 1.01-3.39), having any comorbidity (aRR, 1.93; 95% CI, 1.10-3.41) and the pandemic influenza season (aRR, 2.90 (1.81; 95% CI, 1.81-4.64).

CONCLUSION: Our findings provide significant information regarding influenza burden of disease among pregnant women.