Pregnancy complications and delivery outcomes of pregnant women with influenza

OBJECTIVES: In a previous study, we showed that maternal influenza in pregnancy gives rise to an increase in some congenital abnormality groups. The aim of this study was to ascertain the relationship between influenza during pregnancy and pregnancy complications, and in addition, delivery outcomes particularly preterm birth and low birth weight in newborns. METHODS: The population-based large control (without any defects) data set of the Hungarian Case-Control Surveillance System of Congenital Abnormalities, in which pregnancy complications, gestational age and birth weight are medically recorded, was evaluated. RESULTS: Of 38,151 newborn infants, 1838 (4.8%) had mothers with influenza during pregnancy. The prevalence of pregnancy complications showed no difference between mothers with or without influenza during the study pregnancy. Mothers with influenza in pregnancy had a somewhat higher gestational age (0.1 week) and a lower proportion of preterm births (8.0% vs. 9.2%). These findings were reflected in the mean birth weight (+37 g) and lower proportion of low birth weight newborns (4.7% vs. 5.1%); these differences were explained by confounders. CONCLUSION: Maternal influenza during pregnancy does not increase the prevalence of pregnancy complications and unsuccessful delivery outcomes.