Pronuclear Transfer: The Secret To ‘Three Parent Baby’

Three biological parents, one offspring. Two moms and one dad. Though this sounds almost biblical, it has been made possible through the advancements in gene manipulation over the past few years. Speaking specifically, it can be achieved using the pronuclear transfer technique. Though this venture was not a shot at making a miracle baby, the outcomes in assisted reproductive technology have been nothing short of a miracle. Let’s read on to know further. .

What is pronuclear transfer?

A pronucleus is the stage of fertilisation prior to nuclear fusion, meaning the nuclei of egg and sperm are not entirely fused together.

The mother’s egg is fertilised  by the father’s sperm producing a zygote. The pronucleus from this zygote is removed and transferred to a second fertilised egg(the donor egg) which is devoid of its nucleus. The zygote (from the donor egg) is now implanted into the mother’s uterus.

Need for pronuclear transfer?

We can all mutually agree that the most popular learning from our school has been- mitochondria are the powerhouses of the cell. These tiny cell organelles are also unique in that they have their own genetic material. Mutations in these genes can lead to severe disorders as one grows up, which are grouped as Mitochondrial diseases, and unfortunately the treatment options available for the patients are primarily supportive and not curative. 

Pronuclear transfer has offered a successful solution to parents, especially women, at high risk of transferring such mitochondrial mutations to their children.UK has been the first country to regulate mitochondrial donation. Other methods like mitochondrial spindle transfer have also been attempted in the UK for mitochondrial manipulation

Safety and Ethics Issues

A premature attempt at three parent in-vitro fertilisation, or IVF,  was ooplasmic transfer technology, made in the mid 1990s in the US. The ooplasm is the cytoplasm of the egg. A small amount of ooplasm from the healthy women’s egg was injected into the mother’s egg, followed by fertilisation with the father’s sperm and implantation in the uterus. This, however, had unknown health implications at the time with limited data available for its safety and efficacy and hence its usage was declined.

The three parent IVF raised several eyebrows, especially following Zukin’s  attempt at creating four babies using this technique to treat infertility. The talks of designer babies and its ethical issues were made by the critics of this technology.

However, UK made a landmark in the assisted reproductive technology by introducing laws to guide the use of three parent IVF for treating mitochondrial diseases.

Despite several questions about the ethics surrounding three parent babies, pronuclear transfer holds a promising future when it comes to combating genetic diseases. Though one can’t deny, this could lead to one complicated family tree!


1. Lyndsey Craven et al. Mitochondrial DNA disease: new options for prevention.Hum Mol Genet. 2011 Oct 15;20(R2):R168-74.
2. Craven, L., Tuppen, H., Greggains, G. et al. Pronuclear transfer in human embryos to prevent transmission of mitochondrial DNA disease. Nature. 2010 May 6;465(7294):82-5.
3. Jessica Cussins & Leah Lowthorp (2018) Germline Modification and Policymaking: The Relationship between Mitochondrial Replacement and Gene Editing, New Bioeth. 2018 Apr;24(1):74-94
4. Fischbach RL, Benston S, Loike JD. Creating a three-parent child: an educational paradigm for the responsible conduct of research.  J Microbiol Biol Educ. 2014 Dec 15;15(2):186-90.