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In April, researchers in China reported that they had initiated pregnancies in monkeys through a procedure seemingly much like in vitro fertilization (IVF), in which embryos created in a dish were implanted in the uteruses of cynomolgus monkeys. There seemed nothing remarkable about that — except that this was not genuine IVF, because the embryos had not been produced by fertilization. They had been constructed from scratch from monkey embryonic stem cells, with no egg or sperm involved. They were not real embryos at all, but what many researchers call embryo models (or sometimes “synthetic embryos”). 

The multi-institutional team of researchers, led by Zhen Lu at the State Key Laboratory of Neuroscience in Shanghai, grew the embryo models in vitro to a roughly nine-day stage of development, making them equivalent to what is called a blastocyst in normal embryos. Then they transferred the models into eight female monkeys. In three of the monkeys, the models successfully implanted in the uterus and continued to develop. None of the pregnancies lasted more than a few days, however, before spontaneously terminating.

Meanwhile, other... see more