Flu shot during pregnancy cuts the risk of stillbirth, preterm and small babies, say researchers.
Specifically, the study showed that H1N1 vaccination during the pandemic was associated with a significantly reduced risk of stillbirth, preterm birth and extremely small babies at birth.
Researchers at the Ottawa Hospital Research Institute (OHRI), the CHEO Research Institute and the University of Ottawa (uOttawa) used data from Ontario's birth record database, BORN, to examine 55,570 single-child births that took place in Ontario during the H1N1 pandemic.
The study shows that, compared to pregnant women who were not immunized against H1N1, mothers who received the H1N1 vaccination were 34 percent less likely to have a stillbirth, 28 percent less likely to deliver before 32 weeks, and 19 percent less likely to give birth to a child with a birth weight for gestational age in the bottom third percentile.
"These are all significant results, but especially interesting is the finding that the vaccinated mothers were one-third less likely to have a stillborn child," said lead author Deshayne Fell, an epidemiologist for BORN Ontario.
"This is one of the only studies large enough to evaluate the association between maternal flu vaccination and stillbirth-a very rare event," he added.
The study also found no increase in adverse outcomes for H1N1-vaccinated mothers and their babies during the weeks before and just after birth, also referred to as the perinatal period.
The results were recently published by the American Journal of Public Health.