Maternal and Perinatal Outcomes of Influenza in Pregnancy after Treatment with Oseltamivir

Context: Influenza infection in pregnancy causes 4%-8% case fatality and five times more perinatal mortality. Influenza is a major contributor to mortality in developing countries; however, the morbidity has largely been underestimated. Public health interventions for prevention are also lacking.

Aims: This study aimed to determine the seasonality of influenza in pregnant Indian women and to estimate the maternal and perinatal morbidity after treatment with oseltamivir.

Settings and design: This was a prospective observational cohort study, conducted in a tertiary hospital.

Subjects and methods: Pregnant women with ILI (influenza-like illness) were recruited into Cohort 1 (polymerase chain reaction [PCR] positive) and Cohort 2 (PCR negative). Gestational age-matched asymptomatic controls formed Cohort 3. Women in Cohort 1 received oseltamivir for 5 days. The incidence of small-for-gestational age (SGA) and preterm birth were the primary outcomes. Maternal and neonatal morbidity formed the secondary outcomes.

Statistical analysis: Unmatched (Cohort 1 and 2) and matched analysis (Cohort 1 and 3) were done. Student's t-test and Chi-square test were used to compare between variables.

Results: Year-round incidence of influenza was recorded. Severe illness was more in Cohort 1 compared to Cohort 2 (36.2% vs. 6.3%; P < 0.001). SGA was comparable in all the cohorts (13%). Preterm birth (7.8% vs. 3.3%; P < 0.08; relative risk-2.75) was considerably high in Cohort 1. Secondary maternal and neonatal outcomes were similar between the groups.

Conclusion: Influenza in pregnancy showed year-round incidence and increased maternal and neonatal morbidity despite treatment with oseltamivir. We suggest the need for newer interventions to curtail the illness in pregnancy.