Objective: This feasibility, proof-of-concept study aimed to assess the impact of maternal pre-pregnancy body mass index (BMI) on preterm infant fecal fermentation and microbiome. Study Design: An infant cohort study (n = 54) in the NICU at MUSC from June 2021 to September 2022 was grouped according to maternal pre-pregnancy BMI—normal weight (<25 kg/m²), overweight (25–29.9 kg/m²), and obese (≥30 kg/m²). All fecal samples were subjected to 16s rRNA isolation and analysis, as well as short chain fatty acid (SCFA) extraction and analysis. Results: Preterm infants born to overweight and obese mothers did not have differences in microbial diversities but did have different bacterial taxonomic composition and lower relative abundance levels of taxa than those born to normal-weight mothers. While controlling for covariates, we found SCFA propionic acid to be higher and more significant in infant stools born to mothers with a higher pre-pregnancy BMI. Conclusions: This is a novel study investigating the microbiome and SCFA in premature infants while considering maternal pre-pregnancy BMI. This study adds to the current literature, in that the preterm infant gut is generally lower in microbial diversity which can impact infant health. Thus, it is important to understand the mechanisms necessary to modulate the microbiome of preterm infants to improve their health outcomes.