Reacción a "First results on babies born with pioneering technology that reduces risk of mitochondrial disease"

Advancing with Cautious Innovation and International Consensus. While early clinical results show promise in reducing the level of pathogenic mitochondrial  DNA in newborns, the application of Pronuclear transfer (PNT) raises significant ethical and regulatory questions that must be addressed through both national oversight and international dialogue. From a bioethical standpoint, germline modification—defined as altering genetic material in a way that affects future generations—has long been met with caution. This is because it involves irreversible changes to the human genome, with potential consequences not only for the individuals born from such interventions but also for society’s understanding of what it means to be human.

Pronuclear transfer, however, occupies a unique space in this debate. It targets mitochondrial DNA, which, although essential for cellular energy production, contributes relatively little to traits traditionally associated with identity, such as physical appearance, personality, or intelligence. Because of this limited influence on key phenotypic characteristics, PNT is viewed by some as an acceptable “ethical testing ground” for germline-level intervention. Rather than resorting to high-risk gene therapy after the onset of a hereditary disease, using PNT technology to reduce the likelihood of disease is a more ethically acceptable option. It provides a possible pathway to explore the responsible use of reproductive technologies without crossing the bright-line boundaries typically drawn around nuclear DNA modification.

Nonetheless, mitochondrial DNA modification is not without ethical complexity. Even if its direct functional role is narrower, it still involves heritable changes and the creation of embryos with genetic contributions from three individuals—the intended mother and father, and a mitochondrial donor. This raises questions about identity, kinship, and the rights of the resulting child, especially regarding disclosure and autonomy. Moreover, the long-term health effects of such interventions remain unknown. To prevent a gradual erosion of ethical boundaries, transparent ethical review processes and long-term clinical monitoring must be established as foundational requirements for any country considering the use of PNT.

From a clinical perspective, preimplantation genetic testing (PGT) should remain the first-line option for reducing the risk of mitochondrial disease transmission. PGT is a more established and less invasive method that allows for the selection of embryos with minimal or undetectable levels of pathogenic mitochondrial DNA. In many cases, this approach has proven effective and carries fewer biological and ethical uncertainties than PNT. In contrast, PNT is a more complex and experimental procedure that combines nuclear DNA from the parents with mitochondrial DNA from a donor egg, and it may result in lower fertilization rates or higher embryonic loss. Therefore, in keeping with the precautionary principle in bioethics, PNT should be considered only when PGT is not feasible or has been shown to be ineffective.

The United Kingdom currently leads in the clinical implementation of PNT, having established a strict licensing and regulatory regime through the Human Fertilisation and Embryology Authority (HFEA). The UK’s model reflects a commitment to enabling scientific advancement while maintaining ethical vigilance. However, reproductive technologies such as PNT are inherently transnational. If only a few countries offer access to such procedures, it may prompt “reproductive tourism”, whereby patients travel abroad to seek unregulated or less strictly governed treatments, potentially undermining safety standards and ethical norms.

For this reason, a coordinated international approach is urgently needed. The World Health Organization (WHO) and the World Medical Association (WMA) are well-positioned to initiate global discussions and help formulate shared ethical guidelines and governance frameworks. These discussions should encompass not only scientific and medical dimensions but also social, cultural, and legal implications. Establishing minimum ethical standards and oversight mechanisms will help ensure that the benefits of PNT are pursued responsibly and that global health equity and ethical integrity are preserved.