Summary: A new study reveals that taking antibiotics within the first two years of life is associated with higher childhood body mass index (BMI) and increased obesity risk. Researchers found that early antibiotic exposure raised BMI, and increased the risk of being overweight by 9% and obese by 20%.
No such link was found with antibiotic use before pregnancy, during pregnancy, or at birth. The findings highlight the importance of cautious antibiotic prescribing for young children to help curb rising rates of childhood obesity.
Key Facts:
- BMI Impact: Antibiotic exposure before age 2 raised BMI and obesity risk in childhood.
- Timing Matters: No significant link was found between antibiotics during pregnancy or birth and later BMI.
- Widespread Use: Most young children are prescribed antibiotics within their first two years.
Source: Pediatric Academic Societies
Taking antibiotics within the first two years of life is linked to a higher body mass index (BMI) in childhood, according to a new study.
The research will be presented at the Pediatric Academic Societies (PAS) 2025 Meeting, held April 24-28 in Honolulu.
Researchers found that children exposed to antibiotics in the first two years of life had a 0.067 higher BMI adjusted for age and sex, a 9% greater risk to be overweight, and a 20% greater risk to be obese than children who were unexposed.
Researchers found no correlation between BMI and antibiotic use before pregnancy, during pregnancy, or at birth.
Antibiotics prescribed to young children are prevalent, according to researchers. The majority of children are prescribed antibiotics within the first two years of life.
Approximately one-fourth of children are exposed to antibiotics during pregnancy and one-third during vaginal birth.
“Antibiotic exposure in the first two years of life has a stronger association with childhood weight gain than exposure during pregnancy stages or other early ages,” said Sofia Ainonen, MD, PhD, medical doctor at the University of Oulu in Finland and presenting author.
“Providers need to be cautious about prescribing antibiotics for young toddlers, especially unnecessary antibiotics for upper respiratory tract infections.”
Childhood obesity is an increasing challenge worldwide, with over 159 million school-aged children diagnosed with obesity in 2022.
The study followed 33,095 vaginally born children in Finland to see if antibiotics before pregnancy, during the perinatal period, and after pregnancy was associated with higher BMI at age two and age 12.
About this antibiotics and childhood obesity research news
Author: PAS 2025
Source: Pediatric Academic Societies
Contact: PAS 2025 – Pediatric Academic Societies
Image: The image is credited to Neuroscience News
Original Research: The findings will be presented at the Pediatric Academic Societies (PAS) 2025 Meeting
Abstract
Timing of Early Antibiotic Exposure and the Risk of Being overweight and Obesity in Children
Background
Early antibiotic exposure has been associated with increased weight gain and obesity in children. There is limited evidence concerning the timing of antibiotic exposure and the risk of overweight or obesity.
Objective
Our aim was to find out whether there are sensitive periods of early antibiotic exposure associated with overweight and obesity in children. We set out to compare the effects of antibiotic exposure before pregnancy, during pregnancy, at birth, and in childhood on the subsequent overweight and obesity in children.
Design/Methods
We conducted a population-based register-based cohort study of 33 095 vaginally delivered children born in Finland. We used comprehensive national registers, medical records and electronic growth data.
The timing of antibiotic exposures was: 1) one year before pregnancy, 2) during pregnancy, 3) in the perinatal period and 4) in the first 2 years of life. The outcomes were 1) the body mass index-for-age z-score (zBMI) at 24 months of age and 2) cumulative incidence of overweight and obesity later until the age of 12 years. We used linear mixed model and Cox hazard regression model. Both analyses were adjusted for several covariates.
Results
The study population included 33,095 vaginally born children. The mothers of 12, 869 (39%) children were exposed to antibiotics one year before beginning of pregnancy, 9,073 (27%) of mothers during pregnancy, 6983 (21%) children in the perinatal period, and 22,453 (68%) children in the first 2 years of life.
The antibiotic exposure before pregnancy, during pregnancy, or in the perinatal period were not associated with the subsequent overweight and obesity in children.
Antibiotic exposure in the first 24 months of life was associated with a higher zBMI at two years of age (mean difference of zBMI 0.067 [95 % CI 0.041 to 0.094]) compared to unexposed ones, in analyses adjusted for all covariates. The same was seen in the long-term analysis until the age of 12 years (adjusted HR 1.20 [95% CI 1.10 to 1.31] for obesity).
Conclusion(s)
Exposure to antibiotics before pregnancy, during pregnancy or in the perinatal period were not associated with the overweight or obesity in childhood. Antibiotic exposure in the first two years of life, however, was associated with overweight and obesity.
Studies examining possible causal pathways between early life antibiotics and child overweight and obesity should focus on antibiotics in the first two years of life.
