Better knowledge of the mechanisms that govern embryo implantation in the uterus, besides being of great biomedical interest, also has unquestionable ethical interest. We must not forget the widespread controversy about when human life begins, as one group of experts in this field maintain that it starts when implantation of the embryo is consolidated, towards the 14th day of life (having begun roughly around the 7th day), while others contend that it begins with fertilisation.

The biological mechanisms related with embryo implantation are fairly unknown. Now however, a major step has been taken in relation to this, following the publication of an article in Cell (156; 1032-1044, 2014) by Ivan Bedzhov and Magdalena Zernicka-Goetz.

Interestingly, it was Zernicka-Goetz’s team who, in 2001, demonstrated with a simple but clear experiment that human life begins with the first division of the zygote.

Bedzhov and Zernicka-Goetz have now provided new information on embryo implantation, showing that the blastocyst (the 60-200 cell embryo) that implants in the uterus is transformed from a small ball of cells to a more complex structure. The experiments were conducted in mice. Using a particular technique, they were able to record the entire implantation process, observing how the blastocyst is transformed into a kind of cellular rosette immediately before implanting in the uterus, which occurs on the 4th day of murine (mouse) embryo life. According to Zernicka-Goetz herself, “It´s a beautiful structure. It’s fascinating how beautiful we are then, and how these small cells organise so perfectly to allow us to develop”.