Until now, scientists have unsuccessfully grown human embryos in the lab to study the events that occur during early human development, specifically the time just after fertilisation. Scientists at The Rockefeller University have kept an embryo alive for 14 days outside the uterus, which could provide key insights into the early human development and early pregnancy loss.

The key to this success was to surround the blastocyst or the hollow ball of cells attached to the uterus that allows the embryo to take shape with just the correct chemical environment and scaffolding for it to attach to. In their study published on May 4 in the journal Nature, they state that the embryo showed normal development similar to what is seen in natural development, thereby providing a glimpse of early embryonic development up to 12 days after fertilisation.

However, in accordance with current international bioethical guidelines, the study has been limited to only 14 days. The researchers stopped the experiment even before the embryo showed signs of early nervous system development.


Different cells types are shown above in an early human embryo, 6 days after fertilization. Cell boundaries are indicated in white, cells of the inner cell mass (which will give rise to the embryo proper) are in green, and trophoblast cells (which will give rise to extraembryonic tissues) are in purple and magenta. Credit: Gist Croft, Alessia Deglincerti, and Ali H. Brivanlou/The Rockefeller University

Because of this, the researchers call upon authorities to review this limitation. According to them, more details about embryo development can be discovered without any restraint on embryo research, which could help eliminate pregnancy loss and birth defects completely.

“Now that it has become possible to culture human embryos to the 14-day limit and perhaps beyond, the time is right for the scientific community to educate the public about the potential benefits and to work with regulators on ethical consensus to guide this important research,” says study author Amy Wilkerson, the associate vice president of research support at the university.

The researchers suggest changing the 14-day rule in a way that will further improve research without compromising the ethical aspect of it. Once this changes, further advancing the knowledge regarding human development will soon be possible.