Why we should not extend the 14-day rule

Bruce Philip Blackshaw
Daniel Rodger
The authors respond to McCully’s (2021) arguments for extending the 14-day rule to 28 days. They argue that biomedical advances do not justify changing the rule, since the reasoning of the Warnock Committee remains relevant. The authors maintain their defense of the 14-day rule on the following grounds: 1. The Warnock Committee reasoning was based on maintaining public trust and providing a moral justification for using embryos, concerns that have not changed to date; 2. Extending the 14-day rule would justify previous concerns about a slippery slope; 3. Only recently has it become possible to study the time period between 7 and 14 days of embryo development, so there is still much to learn about this period; 4. The argument that for an embryo to acquire moral status requires successful implantation is flawed, and if this line of reasoning is followed, then there is no point in stopping the time limit at 28 days; and 5. It would appear that if medical technologies continue to develop, we could continue extending the limits of in vitro embryo research.