Background: Maternal influenza infection can impose significant health risks to pregnant women and their neonates.
Objective: The objective of this study was to assess the effect of maternal antenatal influenza vaccination on adverse neonatal outcomes in terms of premature birth, small-for-gestational age (SGA), and low birth weight (LBW).
Material and Methods: The present cross-sectional retrospective study included women who gave birth to their live third trimester neonates at a secondary care hospital in Saudi Arabia after exposure to the 2013/2014 influenza season in any entire trimester of their pregnancy. Neonatal outcomes of women who received inactivated influenza vaccine in their first, second, or early third trimester have been compared to the neonates of women who did not receive the vaccine throughout pregnancy. Data were collected by chart review.
Results: In the present study, 1237 women were included, of these 347 (28.05%) received the trivalent inactivated influenza vaccine during pregnancy. Neonates born to vaccinated mothers were, on average, 97 g heavier (3279.7934 ± 337.6 compared with 3182.5107 ± 424.06, P = 0.001). Adverse neonatal outcomes were significantly lower in the vaccinated group; premature (9.1% compared with 17.6%, P = 0.001), SGA (8% compared with 14%, P = 0.003), and LBW (6.3% compared with 10.4%, P = 0.022). There was no significant increase in birth defects (2.2% compared to 2.6%, P = 0.711). Logistic regression analysis revealed that, compared to the neonates of mothers who received the vaccine, neonates of unvaccinated mothers are at almost two-fold increased risk of being premature (OR = 1.957; 95% CI, 1.3102.923; P = 0.001), 40% risk for SGA (OR = 1.409; 95% CI, 0.8722.275; P = 0.161), and 30% risk for LBW (OR = 1.306; 95% CI, 0.7732.206; P = 0.319).
Conclusion: Maternal antenatal influenza vaccination is associated with reduced adverse neonatal outcomes in terms of premature birth, SGA, and LBW. Moreover, it is associated with having heavier babies, and not associated with increased birth defects.
Key words: Pregnancy, influenza vaccine, neonatal outcomes, premature, birth weight, defects, small for gestational age