The EXTEND system for extrauterine support of extremely premature neonates: opportunity and caution.

Investigators have recently described successful use of an EXTrauterine Environment for Neonatal Development (EXTEND), essentially an artificial womb, to maintain extremely premature fetal lambs ex utero for up to 4 weeks, supporting normal growth and development. The animals were maintained in a fluid environment (Biobag) while nutrition and gas exchange were supported via umbilical catheters and the use of an external membrane oxygenator. The lambs studied correspond to humans at 23-25 weeks' gestation, which is the target range for proposed clinical trials. This new technology offers the possibility of improving outcomes in a patient population with a high rate of mortality and morbidity. However, if safety and efficacy are adequately demonstrated in the lamb model, there remain important ethical considerations worthy of discussion prior to human trials. Moreover, the authors state there is no intention to use EXTEND on patients below the current limit of viability, but this possibility should nevertheless be considered, and should also be the subject of ethical discussion. Analysis of relevant ethical issues, including patient selection, moral status, rights, obligations, and others should precede use of this promising technology in humans.