A new study from Bar-Ilan University's Azrieli Faculty of Medicine has linked reduced weight and height in boys until age six with antibiotic treatments in the neonatal period (within 14 days of birth), though girls did not exhibit this quality.However, for both girls and boys after the age of six, antibiotic use after the neonatal period showed significantly higher body mass index (BMI).The findings, published in the academic journal Nature Communications, sheds light on the long hypothesized physiological effects antibiotics can have during neonatal development, and could be due to changes in the gut microbiome's development. As shown in the study, neonatal antibiotic exposure was observed to be linked to gut microbiome disturbances until the age of two, with the infants' microbiomes being shown to be significantly less rich than the study's control group. However, this seemed to only last six months, by which point the microbiome richness had equalized. And at 12 and 24 months, the richness far exceeded that of the control group.Further experiments also suggested a possible connection between neonatal antibiotic treatment and impaired childhood growth."Antibiotics are vitally important and life-saving medications in newborn infants," said Prof. Omry Koren of the Azrieli Faculty of Medicine at Bar-Ilan University, who led the study together with Prof. Samuli Rautava of Finland's University of Turku and Turku University Hospital. "Our results suggest that their use may also have unwanted long-term consequences which need to be considered."