Nature 458, 147 (12 March 2009) | doi:10.1038/458147b; Published online 11 March 2009

Human rights cannot cover cells that were never in the womb

See associated Correspondence: Wendl, Nature 458, 831 (April 2009)

Patricia Pranke1 & João Carlos Silveiro2

  1. Hematology and Stem Cell Laboratory, Federal University of Rio Grande do Sul, and Stem Cell Research Institute, Av Ipiranga, 2752, 304G, 90610-000, Porto Alegre, Brazil
  2. Stem Cell Research Institute and Silveiro Advogados, Av Dom Pedro II, 1240, 90550-141, Porto Alegre, Brazil


In his contribution to the Commentary 'Your inbox, Mr President', in which leading scientists provided advice to Barack Obama (Nature 457, 261; 2009), George Daley writes of the strong indication that the Obama administration will remove restrictions on federal funding for human embryonic stem-cell research. Although Daley recognizes the vital importance of this innovative research, he also illustrates the potential limitations and legislative or regulatory restrictions.

The controversial and moral question of when human life actually begins is the basis of limitations placed on work such as somatic-cell nuclear transfer or the derivation of new cell lines from embryos discarded from in vitro fertilization procedures. On 29 May 2008, the Brazilian Supreme Court approved legislation allowing stem-cell research. One of the arguments for this approval is that embryos that have already been frozen would never be implanted in the uterus.

Although many people affirm that human life begins when the sperm is impregnated into the egg, either naturally or artificially, they ignore the role of the uterus. Human status is attributed by some to 5-day-old embryos, which consequently would receive the same protection rights as any person. Do frozen and/or inviable embryos, which could never be implanted in a maternal uterus, deserve this status? To begin the process of forming a living human, there must be connection of an embryo to a mother's epithelial cells. This requires the interaction of the embryo with the endometrium (the wall of the uterus).

The Brazilian constitution states that the civil rights of a person begin at the moment of live birth. The law extends these neonate rights from the moment of conception — but only if the baby is born alive. A fertilized egg that is not implanted in the uterus is neither a neonate nor a person. According to traditional Roman law: "Nasciturus pro iam nato habetur, quotiens de commodis eius agitur", which translates as "The unborn child is treated as a child already born in all things respecting its interests". This was presumably conditional on its being born alive. If not, then this protection becomes obsolete.

For a human being to exist and to benefit from civil protection laws, the uterus is a crucial component.