A new study has connected neonatal exposure to antibiotics within fourteen days of birth to a reduction in body mass index (BMI), weight, and height in boys, but not girls, and that reduction continues up to the age of six. Conversely, the research also suggested that antibiotic exposure after the neonatal period but during the first six years of life is linked to a significant increase in BMI in boys and girls. The findings have been reported in Nature Communications.
The study authors noted that antibiotics can have a considerable impact on the composition of the gut microbiome. They suggested that this may be a reason for the reduction in growth and weight in boys that are exposed to antibiotics when they are in the neonatal stage.
In this work, the researchers assessed a group of 12,422 children that were born between 2008 and 2010 in Turku, Finland. None of the children in the cohort had genetic abnormalities or serious diseases that impact growth, and none of them needed to be treated with antibiotics over a long period of time. However, antibiotics had been administered in the first two weeks of life to 9.3 percent of the individuals in the study, or 1,151 infants.
The researchers found that antibiotic-exposed boys, but not girls, had significant reductions in weight throughout the first six years of life compared to unexposed boys, and there were significant reductions in BMI and height between the ages of two and six. The study authors noted, however, that antibiotic use was also much higher in boys, so many more antibiotic-exposed boys were included in the research.
The study also showed that the antibiotics disturbed the composition of the gut microbiome until the children were about two years old. The research also determined that when fecal microbiome samples were transferred from antibiotic-exposed infants to germ-free male mice, there was a reduction in the growth of the mice. That same reduction was not seen in female mice after a fecal microbiota transplant. This adds evidence to the idea that the reductions in weight and height in antibiotic-treated neonatal boys are due to the changes in the microbiome.
"Antibiotics are vitally important and life-saving medications in newborn infants. Our results suggest that their use may also have unwanted long-term consequences which need to be considered," said study co-leader Professor Omry Koren of the Azrieli Faculty of Medicine of Bar-Ilan University.
There are several limitations to this research, which the authors acknowledged. Importantly, it's difficult to ascertain whether the health conditions that led to the use of antibiotics had an influence on development. It's also impossible to directly assess the impact of antibiotic exposure on neonates.