Hospitalisations linked to antibiotics

Children born to mothers who were prescribed antibiotics during pregnancy have a 20% higher risk of subsequently being hospitalised with infection, a joint Australian-Danish study has found.

The study – conducted by the Murdoch Children’s Research Institute (MCRI) in Melbourne and Aarhus University in Denmark – looked at more than 750,000 Danish pregnancies that occurred between 1997 and 2009. The resulting children were followed until they reached 14 years of age (unless death or emigration occurred earlier) and instances of hospitalisation for infection logged against when and if their mothers had received antibiotics during or before pregnancy.

The researchers, led by the MCRI’s David Burgner, found that women who had received antibiotics in the 18 months before falling pregnant, or during the pregnancy itself, gave birth to children with a higher likelihood of subsequently contracting infections that led to hospital stays.

The risks were greatest for children born to mothers who had received more than one course of antibiotics, and those who had received them late in the pregnancy. In this latter category, risks were higher for children born vaginally than those born by C-section.

Denmark enjoys a large, well-regulated and free hospital system, so the scientists had plenty of supporting information to work with during their research. They were able to adjust their findings to take into account potentially complicating data on age, smoking, and mode of delivery.

However, they note that some information was not available – such as the nature and severity of maternal infections, or whether the women completed their prescribed antibiotic courses – and that this places a limitation of the conclusions that can be drawn.

In general, however, the study further illuminates the critical role of maternal microbiomes in kick-starting the gut flora of babies.

It is thought that infant microbiomes may be initially seeded while still in utero. Other studies show that mode of birth directly affects a baby’s microbial load, with vaginal birth bestowing a cargo of gastrointestinal and vaginal flora, while C-section delivery imparts microbes from the skin and the hospital itself.

Women who have to take antibiotics during pregnancy are likely to have their own microbiomes profoundly altered – and consequently pass on a less protective load to their children.

The scientists note that infection is a leading cause of childhood illness and death around the world, but only 20 to 30% of children (in industrialised countries) become sick enough to require hospitalisation, even though the causes of their illness are likely pathogens that colonise most kids.

“The mechanisms underlying this differential susceptibility are largely unknown,” the researchers write. They posit genetic and environmental factors as probable contributors. They add that their findings suggest that antibiotic history should now also be taken into account.

Burgner states that the study should not lead to the conclusion that antibiotics during pregnancy should be avoided. Rather, they should be used with caution.

“Infections during pregnancy are relatively common and should be treated appropriately; some are due to bacteria and will require antibiotics,” he says.

“We need to use antibiotics sensibly in all age groups, including pregnant women. Unnecessary antibiotic use can have effects even in the next generation.”

According to the MCRI, in Australia antibiotics are prescribed in about 12% of pregnancies. It is thought to be one of the highest rates in the world.

The research is published in the International Journal of Epidemiology.