Asian Journal of Medicine and Health

The fetal epigenome is established during periods of extensive cellular differentiation and may record, buffer or transmit information about the maternal milieu. This critical narrative review evaluates evidence that maternal nutrition and metabolic state, environmental toxicants and ambient pollution, and psychosocial conditions alter epigenetic regulation in the placenta, cord blood or fetal tissues. Literature published from January 2000 to 26 May 2026 was identified through accessible scholarly indexes, supplemented by citation searching and verification against authoritative bibliographic records. Evidence was appraised across human observational studies, natural experiments, randomised trials and mechanistic animal models. The strongest replicated human evidence concerns sustained maternal smoking, for which newborn DNA methylation signatures are consistent across cohorts and some marks persist beyond childhood. Nutritional programming is mechanistically compelling, particularly for one-carbon metabolism and severe energy or protein imbalance, but human findings are most persuasive in quasi-experimental settings and at metastable epialleles; routine supplementation and dietary interventions have produced smaller, locus-specific or non-replicated effects. Air pollution, metals, phenols, phthalates and per- and polyfluoroalkyl substances are associated with placental or cord-blood epigenetic variation, yet effect sizes, loci and biological interpretation vary with exposure assessment, gestational timing, tissue composition and co-exposure. Psychosocial studies support stress-responsive placental and hypothalamic-pituitary-adrenal pathways, but candidate-gene associations have not translated into a stable epigenome-wide signature. Across domains, DNA methylation dominates measurement, whereas histone regulation, chromatin accessibility and non-coding RNA remain less comprehensively studied in humans. Most findings establish exposure-associated molecular variation rather than durable, causal programming of organ function or disease. Progress requires longitudinal and diverse pregnancy cohorts, repeated exposure measurement, cell-resolved placental and fetal models, multi-omic integration, functional perturbation and causal triangulation. Epigenetic evidence can clarify biological embedding of prenatal conditions, but it should not be interpreted as deterministic or used to individualise responsibility for structurally patterned maternal exposures.