The dilemma behind "three-parent babies": Why is it difficult for the fourth-generation IVF technology to reach the clinical stage?
Source: LelaiwaPublished: 2025-12-04
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“”,“”.Since in the cytoplasm of an egg donated by a third party, the mitochondria responsible for supplying energy to the cells themselves carry the donor's genetic genes, the embryo formed through this technology not only has the nuclear genes of both parents, but also contains the donor's mitochondrial genes. Research in the reproductive medicine community generally believes that at least 20% of the genetic material in such embryos comes from third-party donors. This characteristic directly touches the three core problems of human reproductive ethics, legal definition and clinical safety.
In the current clinical application of in vitro fertilization technology, three core principles are generally followed: First, the principle of medical necessity, which applies only to patients diagnosed with infertility or couples who have specific genetic disease prevention needs. Second, the principle of ethical compliance, which requires strict adherence to the rules regarding the voluntary and confidential nature of sperm and egg donations, as well as prohibiting the commercialization and misuse of embryos. Third, the principle of safety priority, where the health of both mother and child is considered the top priority. Therefore, treatment options that are more mature and have lower risks are preferred.
,.Ethical torture, security unknown, and legal constraints together constitute three thresholds that are difficult to cross. Although research on this technology has never stopped in the field of reproductive medicine, especially its potential in blocking mitochondrial genetic diseases is still worth looking forward to, for this technology to truly serve human health, it still requires the scientific community, ethics community and legal community. Work together to find a balance point between technological development and human social order on the basis of clarifying technical boundaries, improving safety standards, and building ethical norms. Perhaps in the future, with the deepening of cognition and the improvement of rules, the technical dilemma behind "three-parent babies" will eventually be solved. But for now, relying on mature technology of the first three generations and following strict medical ethics is still the mainstream direction in the field of reproductive assistance.
For more on fertility preparation, second/third-generation IVF, and overseas, U.S., Thailand, Malaysia, America or Cambodia IVF, scan the QR code on the right or call lelaiwa's hotline+852 6145 8043!
In 2016, the birth of the world's first male "three-parent baby" was a sensation in the field of reproductive medicine-Dr. Zhang Jin, a Chinese businessman embryologist, used mitochondrial replacement technology (MRT) to help A patient with a mitochondrial genetic disease successfully gave birth to a healthy baby boy. This breakthrough has brought the fourth generation of IVF technology into the public eye, but ten years later, this highly anticipated technology has never been popularized globally. What is it that makes this technology, which seems to be able to solve genetic problems, fall into a promotion dilemma?
The essence of technology: The “three-parent” characteristics are created through “nuclear-cytoplasmic recombination”
,.Currently, this technology mainly includes two types of key technologies: mitochondrial genome replacement technology (MRT), also known as egg stem cell technology, and its variant germinal vesicle transplantation technology (GVT), commonly known as egg plasma replacement technology. The principles of the two are highly similar. The core operation is to extract the egg cell nucleus from a female egg with mitochondrial defects or aging problems, and then combine it with the cytoplasm of an egg donated by a healthy third-party woman to build a new healthy egg. Finally, fertilization and embryo transfer are completed through the regular IVF process.“”,“”.Since in the cytoplasm of an egg donated by a third party, the mitochondria responsible for supplying energy to the cells themselves carry the donor's genetic genes, the embryo formed through this technology not only has the nuclear genes of both parents, but also contains the donor's mitochondrial genes. Research in the reproductive medicine community generally believes that at least 20% of the genetic material in such embryos comes from third-party donors. This characteristic directly touches the three core problems of human reproductive ethics, legal definition and clinical safety.
Controversial point one: The ethical boundaries are difficult to cross
“”.Human reproduction has long followed the natural law of "parental inheritance", and the emergence of "three-parent embryos" has broken this traditional understanding and triggered a series of in-depth ethical discussions on "definition of the origin of life" and "genetic identity". Some views believe that the intervention of mitochondrial genes may affect the integrity of an individual's genetic characteristics and even pose a challenge to the definition of "parent-child relationship". More importantly, the reproductive medicine community has long reached a consensus: in addition to the clear medical need of "blocking the inheritance of mitochondrial defects", no other reason is enough to support the clinical application of the technology, which fundamentally limits the scope of application of the technology., also sets an ethical red line for commercial abuse.Controversy Point Two: Many uncertainties remain regarding clinical safety
,.Although there have been cases of "three-parent babies" being born successfully, the technology has been used for a short time and long-term safety data is still blank. Mitochondria is the core of cellular energy metabolism, and the synergistic mechanism of its genes and nuclear genes is extremely complex. Whether nucleo-cytoplasmic recombination will cause abnormal gene expression, whether there are potential risks of genetic mutations, and whether these risks will be accumulated and passed on in future generations, have not been fully verified. In addition, there are differences in the genetic background of different individuals, the degree of standardization of technical operations, the precision control of cytoplasmic extraction and nuclear transfer, etc., may affect the healthy development of embryos. These unknown factors have made most medical institutions around the world cautious about their clinical application. attitude.Third point of contention: Legal prohibitions create rigid barriers
,.Currently, only the United Kingdom has passed strict legal restrictions to allow the implementation of MRT technology under certain medical conditions. Almost all other countries have a "red light" on the clinical application of the fourth generation of IVF technology. The attitude of the United States is quite representative: In August 2017, the U.S. Food and Drug Administration (FDA) sent a letter specifically to Dr. Zhang Jin, who implemented MRT technology, clearly stating that the United States strictly prohibited the application of "three-parent technology" in the clinical field of human reproduction. At the same time, it criticized its use of this technology to treat ordinary infertility through marketing means, believing that this exceeded the medical boundaries of technically reasonable medical standards.Current mainstream options: mature and controllable third-generation technologies, with core principles to be followed
,,.The first generation of IVF technology (In vitro fertilization-embryo transfer, IVF-ET) mainly targets women's fallopian tube blockage and achieves pregnancy by transferring embryos after in vitro fertilization; second-generation technology (Intracytoplasmic Single Sperm Injection (ICSI) solves the problem of poor quality of male sperm, injecting a single sperm directly into the egg to complete fertilization; the third-generation technology (Preimplantation Genetic Testing, PGT) carries out genetic testing before embryo transfer. Genetic testing can effectively screen out embryos carrying genetic diseases or chromosomal abnormalities, greatly reducing the risk of transmission of genetic diseases.In the current clinical application of in vitro fertilization technology, three core principles are generally followed: First, the principle of medical necessity, which applies only to patients diagnosed with infertility or couples who have specific genetic disease prevention needs. Second, the principle of ethical compliance, which requires strict adherence to the rules regarding the voluntary and confidential nature of sperm and egg donations, as well as prohibiting the commercialization and misuse of embryos. Third, the principle of safety priority, where the health of both mother and child is considered the top priority. Therefore, treatment options that are more mature and have lower risks are preferred.
,.Ethical torture, security unknown, and legal constraints together constitute three thresholds that are difficult to cross. Although research on this technology has never stopped in the field of reproductive medicine, especially its potential in blocking mitochondrial genetic diseases is still worth looking forward to, for this technology to truly serve human health, it still requires the scientific community, ethics community and legal community. Work together to find a balance point between technological development and human social order on the basis of clarifying technical boundaries, improving safety standards, and building ethical norms. Perhaps in the future, with the deepening of cognition and the improvement of rules, the technical dilemma behind "three-parent babies" will eventually be solved. But for now, relying on mature technology of the first three generations and following strict medical ethics is still the mainstream direction in the field of reproductive assistance.
For more on fertility preparation, second/third-generation IVF, and overseas, U.S., Thailand, Malaysia, America or Cambodia IVF, scan the QR code on the right or call lelaiwa's hotline+852 6145 8043!
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