This systematic review explores the intricate relationship between the maternal microbiome and adverse obstetric outcomes in women with a history of recurrent miscarriages, preterm birth, or stillbirth, collectively known as Bad Obstetric History (BOH). The microbiome, encompassing bacteria, viruses, and fungi, within the reproductive tract is increasingly recognized as a crucial factor in pregnancy maintenance and complications. The study explores BOH's multifactorial causes—genetic, anatomical, endocrine, thrombophilic, immunological, and environmental. Despite one-third of cases being unexplained, it underscores the importance of evaluating uterine macro and microenvironments. Emerging evidence challenges prior beliefs by supporting the existence of an endometrial microbiome, hinting at its impact on pregnancy outcomes. The methodology follows a systematic approach adhering to PRISMA guidelines, incorporating electronic database searches yielding 125 relevant articles, with 47 meeting inclusion criteria. The selected studies focus on human samples from stool, oral, or vaginal swabs, including randomized clinical trials, systematic reviews, and meta-analyses. In conclusion, the review emphasizes the significance of understanding the microbial changes in pregnant females and their potential impact on obstetric outcomes. The findings propose a connection between altered microbiota and maternal complications, highlighting the potential for personalized medicine interventions. Additionally, the study delves into the nuanced relationship between ethnicity, dietary patterns, and the microbiome, underscoring the importance of personalized and culturally sensitive healthcare interventions. Overall, this comprehensive review provides valuable insights into the role of the microbiome in obstetric outcomes, paving the way for future research and targeted interventions to optimize pregnancy outcomes globally.