Artificial Placenta and Partial Ectogenesis for Extremely Preterm Infants: A Narrative Review

Extremely preterm births at the edge of viability are associated with high mortality and significant long-term morbidity. This is largely due to the sudden and involuntary shift from fetal placental support to neonatal lung breathing, accompanied by systemic organ injury. Between 22 and 24 weeks of gestation, the fetal lungs, brain, and metabolic regulatory systems are not biologically prepared for extrauterine life. As a result, extremely preterm infants are highly vulnerable to ventilator-induced lung injury, oxygen toxicity, hemodynamic instability, and inflammatory cascades that contribute to bronchopulmonary dysplasia and neurological injury. Modern neonatal intensive care can provide respiratory, hemodynamic, nutritional, and supportive care; however, it cannot fully reproduce fetal physiology. Artificial placenta and artificial womb technologies, often described as partial ectogenesis, aim to provide extracorporeal gas exchange through the umbilical vessels while maintaining fluid-filled lungs in a closed, thermoregulated, amniotic-like environment to support fetal physiology after delivery. Preclinical ovine models using pumpless arteriovenous circuits and sealed fluid environments have demonstrated the feasibility of supporting fetuses at developmental stages comparable to human periviability for prolonged periods while maintaining stable fetal circulation. However, major translational barriers remain, including reliable umbilical vascular access, development of ultra-low-resistance oxygenators that function at fetal flows and pressures, hemocompatibility and anticoagulation management, infection control during prolonged extracorporeal support, and the inability to replicate the placenta’s endocrine and metabolic functions necessary for normal fetal growth and organ maturation. The ethical implications are also substantial. Partial ectogenesis may alter how clinicians and society approach viability, influence thresholds for resuscitation and periviability counseling, complicate consent in high-stress emergency settings, and generate distributive justice concerns if access remains limited to highly specialized centers. This narrative review summarizes the physiological rationale, major preclinical evidence, translational challenges, and ethical considerations surrounding artificial placenta and partial ectogenesis technologies for extremely preterm infants.