Antibiotic Exposure During the First 6 Months of Life and Weight Gain During Childhood

Prerana Patel, Mercer University College of Pharmacy


In an annual report published by The Centers for Disease Control and Prevention, Moxatag® (amoxicillin) was the most frequently dispensed prescription antibiotic to infants (ages 0-23 months) and children (age 2-11) in 2010. [1]

Guidelines from American Academy of Pediatrics do not mention weight gain in infants who were exposed to antibiotics during the first six months of life. [2]

Title: Antibiotic Exposure During the First 6 Months of Life and Weight Gain During Childhood [3]
Design Multicentre, retrospective, longitudinal cohort study, N = 38,614
Objective To assess the association between early-life antibiotic exposure and childhood weight gain
Study Groups Singletons (n = 38,522); twins (n = 92)
Methods Data was collected from 30 pediatric primary care practices in three states: southeastern Pennsylvania, southern New Jersey, and northern Delaware.  Retrospective chart reviews were done to collect and analyze data.
Duration November 1, 2001 to December 31, 2012
Primary Outcome Measure Weight measured at health visits from age six months through eight years of life
Baseline Characteristics Characteristics from singleton population
  Antibiotic Exposure in First 6 months  

(n = 5287)


(n = 33,235)


(n = 38,522)

Male, (%) 2,891 (55) 16,538 (50) 19,429 (50)
Black (%) 1,023 (19) 11,860 (36) 12,883 (33)
Nonblack (%) 3,545 (67) 16,950 (51) 20,495 (53)
Unknown (%) 719 (14) 4,425 (12) 5,144 (13)
Birth Weight, mean (SD), kg 3.47 (0.46) 3.38 (0.46) 3.40 (0.46)
Characteristics from twin population
  n = 92 (42 twin sets)
Female, (%) 38
Birth weight, mean, kg 2.8
Age at exposure, mean, months 4.5
Results Results from singleton population
  No. of patients Difference in rate of weight gain associated with exposure, % (95% CI) p value
6-month exposure
No antibiotic 33,235  
Any antibiotic 5,287 0.7 (-0.1 to 1.5) 0.07
2-year exposure
No antibiotic 8,969  
Any antibiotic 18,809 2.1 (0.8 to 3.3) 0.001
Results from twin population
  Weight change, kg 95% CI, kg p value
Difference between exposed and unexposed twin -0.09 -0.26 to 0.08 0.30
Exposure in first 24 months -0.11 -0.28 to 0.05 0.18
Adverse Events Common Adverse Events: N/A
Serious Adverse Events: N/A
Percentage that Discontinued due to Adverse Events: N/A
Study Author Conclusions Exposure to antibiotics within the first six months of life compared with no exposure was not associated with a statistically significant difference in weight gain through age seven years.

This study analyzed patients during the first six months of life because this was the time period in which antibiotics were found to increase adiposity in animal experiments.  Twins were included to help examine the influence of environment and genetics.  Weight was used as a measure over body mass index (BMI) because length is measured during the first 24 months rather than height.  The fact that BMI (a unit used to measure adiposity) was not used limited the study and did not allow it to address adiposity; a proper conclusion cannot be drawn about overall weight gain from antibiotic use.



[1] Bloom B, Cohen RA, Freeman G. Summary health statistics for US children: National Health Interview Survey, 2010. National Center for Health Statistics. Vital Health Stat 10(250). 2011. Available at:

[2] Wald ER, Applegate KE, Bordley C, et al. Clinical practice guideline for the diagnosis and management of acute bacterial sinusitis in children aged 1 to 18 years. Pediatrics. 2013;132(1):e262-80.

[3] Gerber JS, Bryan M, Ross RK, et al. Antibiotic Exposure During the First 6 Months of Life and Weight Gain During Childhood. JAMA. 2016;315(12):1258-1265. doi:10.1001/jama.2016.2395.


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