Josephine Johnston, director of research and a research scholar at The Hastings Center, has joined two co-authors in proposing a reexamination of an internationally recognized rule limiting in vitro research on human embryos to 14 days post-fertilization. Writing in the journal Nature, they respond to technological advances that have nearly doubled the length of time that embryos can be sustained in vitro, from about seven days until 12 to 13 days.
These advances “put human developmental biology on a collision course with the ‘14-day rule’ – a legal and regulatory line in the sand that has for decades limited in vitro human-embryo research to the period before the ‘primitive streak’ appears,” they write. The formation of the primitive streak is biologically significant because before this point, embryos can split in two or fuse together.
The authors note that while some people believe the primitive streak is also a morally significant moment in embryo development, the public’s views differ widely on the stage at which embryos and fetuses attain sufficient moral status that research should be prohibited. Their analysis of policy development in this area shows that the 14-day rule “was never intended to be a bright line denoting the onset of moral status in human embryos.” Rather, its chief goals were to carve out a space for embryo research to go forward while also accommodating many of these diverse moral views.