For MIT Technology Review. Cassandra Willyard surveys the state of rapidly advancing artificial womb research. As a promising prototype nears readiness for trials with human embryos, researchers and bioethicists are weighing potential implications on child-rearing. “The most challenging question to answer is how much unknown is acceptable,” says FDA neonatologist An Massaro to Willyard, of concerns that include gauging risk for premature infants and shifting discourse about a woman’s right to choose.