Impact of prebiotics, probiotics, and postbiotics on maternal and fetal health: mechanisms, efficacy, and safety across pregnancy

Abstract

Microbiome-directed biotics are gaining attention in obstetrics. This review clarifies terminology, mechanisms, clinical effects, and safety for prebiotics, probiotics, and postbiotics. Prebiotics are nondigestible substrates that are selectively used by host microbes to confer health benefits. Probiotics are defined as live microorganisms that improve health when given in adequate amounts. Postbiotics are preparations of nonviable microbes or their components that trigger beneficial responses. We summarize how these agents may influence maternal and fetal physiology across gut, immune, metabolic, vaginal, placental, and human milk contexts. In the gut, they reshape short-chain fatty acid and bile acid pools, modulate enteroendocrine hormones, and recalibrate basal immunity. They also tighten epithelial junctions and stimulate goblet cell mucin, which reduces microbial translocation, endotoxemia, and vascular strain. In the vaginal and urogenital niches, lactobacilli maintain acidity, suppress pathobionts, and may lower colonization risk. At the placenta and in milk, microbial metabolites and immune mediators, including human milk oligosaccharides and secretory IgA, carry maternal cues that shape fetal and neonatal development. Safety profiles differ by class. Prebiotics are generally well tolerated, with dose-dependent gastrointestinal symptoms most common. Probiotics require strain-level validation, viability control, and contaminant-free production. Postbiotics need to be verified inactivation and structural characterization. IMPACT: Provides a comprehensive, mechanism-based overview of how prebiotics, probiotics, and postbiotics influence maternal and fetal health across multiple physiological systems. Clarifies definitions, safety profiles, and quality standards for biotics in pregnancy, addressing current inconsistencies in research and commercial products. Integrates emerging evidence on postbiotics and vertical microbial transmission, offering a timely framework for future clinical applications and regulatory guidance.