For several decades, scientists have reasoned that stem cells—and human embryonic stem cells (hESC) especially—have the potential to improve human health. In particular, research indicates that the properties unique to hESC (e.g., plasticity, potency) can benefit our understanding of, and approaches to, regenerative medicine and embryology. For instance, understanding how these cells might (i) mitigate or treat diseases such as Alzheimer’s, Parkinson’s, cancer, and diabetes, and (ii) produce vital insights into human development, is a priority within the scientific research enterprise, but one whose methodologies and ethics should be thoroughly monitored and reviewed in accordance with advances in medicine.

In this spirit of inquiry, I have been following the ethics of human embryonic stem cell research for about a decade. During this period, guidelines on hESC research have been issued by a number of different governments and organizations, and various viewpoints and practices have emerged. Intrigued by these developments, my colleagues and I at the California Department of Public Health mapped out (pdf) the status of such hESC research regulations and policies near the end of the 2000s. Our research indicated that a patchwork of standards (and in many jurisdictions, an absence of guidelines, regulations, or restrictions altogether) exists both domestically and internationally.

Despite this emerging hodgepodge, one longstanding rule grounding the regulatory and ethical landscape of hESC research has remained constant since its inception in the early 1980s: the so-called fourteen-day rule (pdf), which limits research on human embryos to the first fourteen days of their development.[i] The fourteen-day rule is an internationally recognized guideline; while it is not officially enforceable, at least twelve countries—including the United States, United Kingdom, Canada, Australia, China, and India—have consistently upheld this standard. The International Society for Stem Cell Research’s (ISSCR) recently revised guidelines, which are geared toward the global scientific research community, continue to employ the rule.[ii]

In recent months, however, the rule has been called into question, since researchers have discovered how to keep embryos alive longer in the lab. Specifically, researchers have reported sustaining human embryos in vitro up to thirteen days—a noteworthy feat, since it is the first time that researchers have cultured human embryos in vitro for more than nine days, and sustaining them beyond seven-to-nine days is uncommon. While these accomplishments have the potential to provide scientists with an unprecedented lens through which early human development can be investigated—e.g., origins of miscarriage and birth defects, and use of stem cells for disease treatment—leading bioethicists assert that the advances are “on a collision course” with the fourteen-day rule.

In light of the ongoing developments in embryo research, the scientific research community and research oversight organizations are poised to consider whether the rule should be reconceptualized to accommodate research activity beyond the fourteen-day mark. Of an important note, the fourteen-day rule was established during a time when it was impossible to keep embryos alive in the lab for that long. Indeed, rather than formulating itself as a fixed moral truth, the fourteen-day rule has served as a public policy guidepost, aimed at establishing a balance between permitting research activities and accommodating manifold moral anxieties. It became a standard component of embryo-research oversight through the complex deliberations of multiple international committees over decades.

Undoubtedly, this is a complex debate that is still unfolding, and one that ultimately will be best decided with deference to international coordination and the accommodation of varying moral positions and principles. Given these collective concerns, is an allowance of more time prudent? And even if that is determined to be the proper course of action, just how many more days should be permitted, and how arbitrary of a calculation would this be? In any event, an ethical approach to overseeing new and developing forms of embryo research should be calibrated carefully and methodically, both at home and abroad, and in consultation with bioethicists, researchers of early human development, policymakers, and the public.

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Matthew Dias is a research ethicist at the New York State Psychiatric Institute IRB and Associate Fellow for Columbia University’s Precision Medicine: Ethics, Politics, and Culture Project.

[i] Under the rule, in vitro research on human embryos is limited to fourteen days post-fertilization. This research is permitted before the cutoff date at fourteen days and prohibited thereafter. 

[ii] The guidelines continue to invoke the rule, albeit with the inclusion of additional language supporting research oversight with respect to new forms of embryo research.