Study: Antibiotic exposure before age two linked to childhood obesity

(Press-News.org) 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.

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EDITOR:
Dr. Sofia Ainonen will present “Timing of Early Antibiotic Exposure and the Risk of Overweight and Obesity in Children” on Sun., April 27 from 1:30-1:45 PM ET. 
Reporters interested in an interview with Dr. Ainonen should contact Amber Fraley at amber.fraley@pasmeeting.org.
The PAS Meeting connects thousands of pediatricians and other health care providers worldwide. For more information about the PAS Meeting, please visit www.pas-meeting.org.

About the Pediatric Academic Societies Meeting
Pediatric Academic Societies (PAS) Meeting connects thousands of leading pediatric researchers, clinicians, and medical educators worldwide united by a common mission: Connecting the global academic pediatric community to advance scientific discovery and promote innovation in child and adolescent health. The PAS Meeting is produced through the partnership of four leading pediatric associations; the American Academy of Pediatrics (AAP), the Academic Pediatric Association (APA), the American Pediatric Society (APS), and the Society for Pediatric Research (SPR). For more information, please visit www.pas-meeting.org. Follow us on X @PASMeeting and like us on Facebook PASMeeting.

Abstract: Timing of Early Antibiotic Exposure and the Risk of Being overweight and Obesity in Children

Presenting Author: Sofia Ainonen, MD, PhD

Organization
University of Oulu

Topic
Infectious Diseases

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.

Tables and Images
Figure 1. Mean difference of zBMI at 24 months of age according to early antibiotic exposure.png
Figure 2. Overweight in childhood.png
Figure 3. Obesity in childhood.png

END