(HealthDay News) – Pregnant women vaccinated for H1N1 influenza during their second or third trimesters were less likely to give birth before 32 weeks’ gestation, have a small-for-gestational-age (SGA) baby, or have a stillbirth, compared with those who were not vaccinated, according to research published in the June issue of the American Journal of Public Health.

To compare outcomes between women who received an H1N1 vaccination during pregnancy with those who did not, Deshayne B. Fell, of the Better Outcomes Registry & Network in Ottawa, Canada, and colleagues utilized a population-based perinatal database of 55,570 single births. Specific outcomes studied included preterm birth (PTB), SGA births, infants born with a five-minute Apgar score below 7, and fetal death.

A total of 42% of mothers received an H1N1 vaccination during pregnancy. Overall, the researchers found that H1N1-vaccinated mothers were 10% and 19% less likely to have a SGA infant based on the tenth and third growth percentiles, respectively; 27% less likely to have a PTB less than 32 weeks’ gestation; and 34% less likely to have a stillbirth.

“Our results, obtained with a large birth cohort during a contemporary influenza pandemic in which there were unprecedented rates of maternal vaccination and a strong match between the vaccine and circulating influenza virus, suggest that maternal H1N1 influenza vaccination in the second or third trimester of pregnancy was associated with a reduced risk of PTB at less than 32 weeks, SGA neonates, and fetal death,” the authors write.

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