New Australian research has found if women take antibiotics while pregnant, there is a 20 per cent increased risk of their baby or child being hospitalised for an infection, compared with those children whose mums did not take the medication.

Professor David Burgner, from the Murdoch Children’s Research Institute, conducted the study, which looked at data from more than 750,000 pregnancies from 1997 to 2009 in Denmark.

Scientists crosschecked birth records with the mother’s antibiotic use, and hospital admissions of children with infections.

“We found children born to mothers who were prescribed antibiotics during pregnancy may have up to a 20 per cent higher risk of being hospitalised with infection,” he said.

They found the more antibiotics the mum took and the closer it was to the delivery date, the greater the risk.

“Males were at higher risk of infection if their mothers had taken antibiotics and the increased risk for both genders persisted throughout childhood,” he said.

But researchers stressed the findings needed to be interpreted with caution.

Lead author Dr Jessica Miller said researchers were not exactly sure of the cause of the higher risk.

They said it could be that the antibiotics impact the make-up of the bacteria in the mother’s gut, known as the gut microbiome.

“Impact on the gut microbiome could increase the susceptibility to infections in early childhood, possibly by suboptimal development,” she said.

The way the baby is born also made a difference, with vaginally born babies at a slightly higher risk of developing infections.

The reason is that if it is a vaginal delivery, babies get exposed to their mother’s microbiome, while babies born by caesarean do not.

Australian Medical Association president and obstetrician Dr Michael Gannon said doctors could not stop giving pregnant women antibiotics.

“Pregnant women do need to take antibiotics for infections such urinary tract infections, or if they’re having surgical procedures,” he said.

“But it’s highly plausible that antibiotics could change the mother’s bacteria.”

Professor Burgner said the findings suggest taking antibiotics while pregnant may have longer-term consequences for both mothers and babies.

“If it is the gut microbiome that’s affected, you could intervene and give the mother and baby probiotics,” he said.

But he cautioned there was not enough scientific evidence yet to recommend probiotics to reduce the risk of childhood infection.

Researchers found that in children from newborns up to the age of 14, those born to women prescribed antibiotics closer to birth, or prescribed more than one antibiotics course during pregnancy, had an even greater risk of infection.

Senior research chemist from Centre for Superbug Solutions at the University of Queensland, Dr Mark Blaskovich, said the study highlighted the associated and unexpected hazards caused by taking antibiotics.

“One side effect is that antibiotics can kill off the good bacteria that naturally live in your body, particularly in the gut,” he said.

“The authors have found that this ‘microbiome-altering’ effect, caused by antibiotics taken during pregnancy, can be passed on and compromise the health of the resulting child throughout their childhood.”

He said while the increased risk was not large, it illustrated there could be unintended and potentially long-term consequences with antibiotic use.

The research was published in the International Journal of Epidemiology.

– ABC