Feto-maternal biology and ethics of human society

The embryo is a semi-allograft in the maternal organism because half of its genetic material comes from the father. However, instead of being rejected by the maternal immune system, it is tolerated and develops in the uterus [1].During early embryogenesis, the trophoblast of the external layer of the morula-blastocyst makes direct contact with the uterine wall (blastocyst implantation). In human pregnancy, the trophoblast invades the uterine mucosa and vessels, establishing very intimate contact with the mother (hemochorial placenta). Therefore, the trophoblast and maternal uterus, including immune and non-immune cells of the mucosa and vessels, form the feto-maternal interface, in which tolerance mechanisms are active [2].Ever since Sir Peter Medawar brought the topic of survival of the semi-allogenic fetus in the maternal uterus to the attention of scientists, various studies have sought to throw light on the biochemical and molecular mechanisms that permit this apparent immunological paradox [3,4]. A key role has been attributed to the secretion of a broad array of soluble molecules with autocrine/paracrine action, including growth factors, cytokines and hormones [5]. These substances are produced at the feto-maternal interface by both embryonic and maternal tissues, and they act on specific membrane receptors expressed by complementary tissues [6]. Thus, mother and embryo interact via specific tissues (trophoblast and uterus) in a reciprocal exchange of molecules that act as communication signals. This interactive relationship between the embryo and the mother has the characteristics of a true dialogue: a dialogue that uses molecules instead of words and that takes place in a common language, comprehensible to both mother and embryo.The feto-maternal dialogue begins very early in embryonic development, initiated by the trophoblast via secretion of molecules such as hCG which act on the mother to create a uterine environment favorable to implantation [7]. The ute