Amniotic Fluid and Ocean Water: Evolutionary Echoes, Chemical Parallels, and the Infiltration of Micro- and Nanoplastics

The hypothesis of abiogenesis proposes that life originated in the aquatic environments of early Earth, approximately 3.8–4.0 billion years ago. These ancient oceans, often termed the “primordial soup,” contained a complex mixture of dissolved ions—including sodium, chloride, potassium, calcium, magnesium, sulfate, and bicarbonate—regulated by geochemical and hydrothermal processes. Primitive cells developed homeostatic mechanisms to maintain a stable internal environment, despite external fluctuations. The cell membrane, composed of a lipid bilayer with embedded proteins, regulated ion transport and sustained electrochemical gradients essential for cellular life. Amniotic fluid (AF) recapitulates these evolutionary and physiological principles, providing a stable aqueous environment for fetal development. The chemical similarities between amniotic fluid and seawater reflect a phenomenon of phylogenetic conservation and ontogenetic recapitulation. However, prenatal exposure to environmental toxicants—including heavy metals, persistent organic pollutants, endocrine disruptors, and recently, micro- and nanoplastics (MNPs)—poses a significant threat to maternal and fetal health. These MNPs, widely distributed in marine ecosystems, have now been detected in the human placenta, amniotic fluid, and other organs. This review underscores the interconnectedness of environmental and human health, as framed by the One Health paradigm. The amniotic fluid, as a biological ocean for the developing fetus, must be protected just as we strive to preserve our planet’s oceans. Both are reservoirs of life—evolutionarily linked and mutually dependent.