Maternal Organ Growth: How the Adult Intestine Remodels During Pregnancy and Lactation

Adult organs exhibit remarkable plasticity, dynamically adjusting their size and function to meet physiological demands. The small-intestinal epithelium, one of the most rapidly renewing tissues in mammals, undergoes extensive growth and remodeling in response to diet, injury, microbiota changes, and reproduction. Reproduction is an energetically demanding process that requires precise regulation of maternal physiology to support fetal development and neonatal growth. In many mammals including humans, pregnancy induces systemic changes in hormones, metabolism, and immunity. At the organ level, pregnant and lactating females show increases in intestinal size across species such as mice, rats, sheep, and pigs-a phenomenon first documented nearly a century ago. However, the molecular mechanisms governing maternal intestinal remodeling during reproduction, and its physiological significance, remained unclear until recently. Emerging studies, including our recent work, have begun to reveal the cellular changes, molecular mechanisms, and triggers underlying this adaptive growth. This review summarizes current knowledge of intestinal epithelial plasticity in the context of reproduction, integrating findings from both reproductive and non-reproductive settings. Understanding how the adult intestine adapts to physiological challenges offers valuable insights into developmental biology and has important implications for maternal metabolic health.