Children whose mothers were prescribed antibiotics during pregnancy face up to a 20 per cent higher risk of being hospitalised for infections, a new study shows.
The findings suggested antibiotics alter the "good" gut bacteria babies acquire from their mothers, affecting their immune development and leaving them more susceptible to infection, according to the Australian and Danish researchers.
The analysis of 750,000 pregnancies between 1995 and 2009 found 18 per cent of mothers had at least one antibiotic prescription during pregnancy. More than 28 per cent of children (222,524) were hospitalised for infection by the time they were 14 years old.
The study published on Monday in the International Journal of Epidemiology found babies born vaginally had a higher risk – particularly for gastrointestinal infections – compared with those born via caesarean when mothers had been prescribed antibiotics in pregnancy.
Roughly 20 to 30 per cent of children in developed countries are hospitalised at least once with an infection. An estimated 12 per cent of Australian women are prescribed antibiotics in pregnancy.
Vaginally born babies acquired their microbiome from their mother's gut and birth canal, while caesarean babies picked it up from their mother's skin and the hospital environment.
Antibiotics were known to affect the gut microbiome, which was vital to immune development in early life.
The authors hypothesised that antibiotics during pregnancy could cause an imbalance in the microbiota, which mothers then passed onto their babies, increasing the risk of infection.
The closer the antibiotics were prescribed to birth, the higher the risk, reported the researchers, led by the Murdoch Children's Research Institute.
The study did not show a causal link and also found children born to mothers who were given antibiotics before conception also had an increased risk of infection of 10 per cent, suggesting genetic and environmental factors also played a role.
The results were not a signal to stop using antibiotics in pregnancy, but a reminder that antibiotics should be prescribed only when appropriate, senior author David Burgner said.
"We need to use antibiotics sensibly in all age groups, including pregnant women," Professor Burgner said.
"Unnecessary antibiotic use can have effects even in the next generation."
A study published last year found Australian babies were prescribed antibiotics at some of the highest rates in the world, many for conditions that did not require them. Roughly half the babies were given antibiotics in the first year of life and more than a quarter were given multiple prescriptions, the study of 660 children found.
The World Health Organisation has described antibiotic resistance as a "global health emergency".
"Antibiotics are incredibly important drugs, but they are widely overused, which is threatening their continued effectiveness," said Dr Mark Blaskovich, senior research chemist at the University of Queensland's Centre for Superbug Solutions.
He said the study highlighted the associated and unexpected hazards caused by taking antibiotics.
"Although the effect was not large (about 20 per cent more infections), it does illustrate that there are unintended and long-term consequences to antibiotic usage," he said.