The human gut microbiota encompasses a diverse ecosystem with hundreds if not thousands of microbial species, with relative proportions of different taxa varying both between and within individuals over their lifetimes. Intestinal microbes interact with the central nervous system while playing important roles in host immune and metabolic function. Infants first acquire maternal microbiota during delivery, with mature structure and composition established during the first few years of life. Early childhood therefore serves as a critical window for microbiota development during which the intestinal ecosystem is especially vulnerable to disruption from antibiotics. Research has linked pediatric antibiotic use with long-term metabolic and immune conditions such as obesity, irritable bowel syndrome, asthma, and allergies. This systematic review compiles all studies available on PubMed investigating the link between early childhood antibiotic exposure and risk of obesity later in life. Results were analyzed by characteristics including exposure age, number of exposures, sex, and type of antibiotic. Earlier antibiotic administration and number of administrations were associated with higher risk of obesity, as were broad-spectrum relative to narrow spectrum antibiotics. Exposed boys were also at higher risk of obesity than girls. The increased risk of obesity resulting from antibiotic exposures was estimated to be 5% using a weighted average calculation. An attributable fraction of US obesity to childhood antibiotic exposure was then calculated using state-level population and prescription data. Finally, the total financial burden of antibiotic prescriptions on the US healthcare system was produced based on existing estimates of the economic burden of obesity.