Early antibiotic exposure linked with reduced growth in boys

Giving newborn baby boys antibiotics could stunt their growth in the early years of life, a new study suggests.  

Antibiotic treatment within 14 days of birth is linked with reduced weight and height in boys – but not girls – up to the age of six, experts found. 

The researchers think the differences may result from changes in the development of the gut microbiome – the trillion-strong community of beneficial microorganisms. 

However, antibiotics administered to babies older than 14 days could have the opposite effect, the research team also found. 

Antibiotic use after the neonatal period (the first 28 days of life) but during the first six years of life was linked with higher body mass index, in both boys and girls. 

Exposure to antibiotics in the first days of life is thought to affect various physiological aspects of neonatal development, suggesting they should not be administered without good cause.

But the additional finding suggests this threat is nullified for babies aged 28 days or older. 

‘Antibiotics are vitally important and life-saving medications in newborn infants,’ said study author Professor Omry Koren at the Azrieli Faculty of Medicine of Bar-Ilan University. 

‘Our results suggest that their use may also have unwanted long-term consequences which need to be considered.’ 

If a newborn baby is suspected to have a bacterial infection, they will swiftly be given antibiotics, 

Newborn babies have immature immune systems which make them vulnerable to infection, requiring the use of antibiotics.  

Most premature babies – about 80 per cent – are given antibiotics in their first weeks of life to protect them from potentially fatal bacterial infections. 

The use of antibiotics in newborn babies during the first weeks of life has already been reported to lead to alterations in the composition of the gut microbiome. 

However, the long-term consequences of this exposure are unknown. 

To learn more, the team investigated the association between antibiotic exposure during the neonatal period (within the first 14 days after birth) and child growth until the age of six in a cohort of 12,422 children born between 2008 and 2010 in Turku, Finland. 

The babies had no genetic abnormalities or significant chronic disorders affecting growth and did not need long-term antibiotic treatment. 

Antibiotics had been administered within the first 14 days of life to 1,151 (9.3 per cent) of the 12,422 babies.

By using a statistical score based on growth charts, the authors found that boys (but not girls) in their sample who had been exposed to antibiotics when they were neonates (when they were 14 days old or less) exhibited lower weights and heights up to the age of six compared to those who were not. 

They also exhibited significantly lower height and body mass index (BMI) between the ages of two and six. This observation was replicated in a German cohort. 

Further, antibiotic exposure during the first days of life was found to be associated with disturbances in the gut microbiome up until the age of two. 

Infants exposed to neonatal antibiotics exhibited significantly lower gut microbiome richness as compared to non-exposed infants at the age of one month. 

Interestingly, at the age of six months, the infants treated with antibiotics as neonates reached the bacterial richness level of a control group of infants, who not exposed to antibiotics as neonates.

Later, at the ages of 12 and 24 months, the antibiotic-treated subjects gained significantly higher levels of bacterial richness as compared to the control subjects.

In separate experiments, the authors transplanted microbiota in faecal samples from antibiotic-exposed and non-exposed infants to germ-free mice. 

In male mice, those that received a microbiota transplant from infants one and 24 months after antibiotic treatment were found to have impaired growth. 

No changes were observed in female mice, meanwhile.

Early antibiotic exposure is associated with long-term changes in the gut microbiome, which may result in reduced growth, the authors conclude. 

‘The potential causal link between neonatal antibiotic exposure and impaired childhood growth may be mediated by antibiotic-induced perturbations of the developing intestinal microbiome,’ say the research team in their paper, published in the journal Nature Communications. 

‘Intestinal microbes reportedly play essential roles in the digestion of dietary compounds and modulate intestinal energy harvest as well as host energy metabolism and satiety.’

Researchers note the limitations of their study, meaning that the results should be interpreted with caution. 

For example, the underlying causes and symptoms in newborn babies that lead to antibiotic use may affect height and weight gain in early life.      

In 2018, it was reported that infants given antibiotics and antacid medications are up to 400 per cent more likely to develop allergies as children.

The researchers, from the Uniformed Services University of the Health Sciences, in Bethesda, Maryland analysed data of 792,130 children.

They found those given antibiotics in the first six months of their lives had an increased risk of a range of allergies between 14 and 100 per cent (depending on the allergy).

For those that took antacids, rates were even higher, with increases of 12 to 140 per cent for one kind of antacid, and between 12 and 400 per cent for another.

The authors of the large study stressed that, given their findings, antibiotics and antacids should only be prescribed to infants when absolutely medically necessary.