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Can society accept '3-parent' offspring?

Published on Oct 24, 2012 3:09 PM

IN BRITAIN, there is an ongoing public consultation till December over a fertility treatment that involves two biological mothers and one biological father.

This technology will help mothers with defective mitochondria, which are tiny, precisely functioning "machines" found in every cell that generate energy in a form called ATP that cells can use. Without mitochondria and thus ATP, life would not be possible.

All mitochondria sit in a cell's cytoplasm, the jelly-like soup holding a cell's contents together. Cytoplasm nourishes the nucleus in the cell's centre.

The nucleus carries chromosomes containing DNA, or the 20,000 genes that code for most of our human traits. This nuclear DNA comes from both parents.

Uniquely, mitochondria are the only sites outside the nucleus that also carry DNA. But this mitochondrial DNA (mDNA) differs from that found in the nucleus. It carries only 37 genes, which code for various metabolic purposes, so mDNA mutations can lead to muscular dystrophy, epilepsy, strokes, mental retardation and so on.

Uniquely, mDNA is derived from the mother only. In women whose eggs have faulty mDNA, serious conditions may be passed to their offspring. One in 6,500 children worldwide is afflicted by this.

To overcome this, defective mDNA must be removed from the mother's egg during in-vitro fertilisation (IVF) and substituted with healthy mDNA from a donor egg. But the baby thus made would have nuclear DNA from its father and mother, as well as mDNA from the woman egg donor.

Britain announced in 2008 it had made 10 such "trigamous" or three-gamete human embryos, which were never implanted in a womb. But in 2002, scientists in Guangzhou, China had taken an egg from a barren woman and fertilised it in a petri dish with her husband's sperm. Next the fertilised nucleus was removed from her egg and transferred into a donor egg emptied of its own nucleus (along with its nuclear DNA).

The hybrid egg - with the father and mother's DNA combined in the nucleus with the donor egg's healthy mDNA in the cytoplasm outside the nucleus - was then implanted into the mother's womb, which became a twin pregnancy. Sadly, she lost both at the 24th and 29th weeks, which however were tested to be genetically normal. So the technique is clearly viable.

No genes are altered in this process: Some bad ones are just swopped for some good ones. But if the "trigamous" offspring is female, she can also theoretically transmit the donor's mDNA to future generations in perpetuity.

In 2005, Australia reviewed its laws and re-affirmed its ban on making "embryos with more than two genetic parents... for reproductive purposes". Law-breakers may be jailed up to 10 years.

It is banned in the United States too, a ban that is unusual given that the fertility industry is self-regulated in most countries as reproductive liberty is highly cherished in the West. The industry sees bans only on human cloning and rules on experimentation with human embryos. Most fertility treatments are quickly pressed into service without having their safety firmly established. So why is this technique so unsettling?

The reason is that it involves transferring one nucleus (a fertilised one in this case) into an "empty" egg, this being the crucial step in cloning. Once the technology is approved for use, a scofflaw scientist could take the nucleus from a cell of some organ of an adult or child, transfer it into an "empty" egg and the hybrid egg would start dividing as if it were fertilised. This embryo could then be implanted in a womb and the human clone brought to term.

Cloning is already banned by law in Singapore and elsewhere. If this trigamous technology is made available without legalising human cloning too, some infertile couples could be helped. The fear of renegade cloners abusing it should not hinder women with mDNA issues from having babies.

The fear of cloning aside, a technology that results in possibly three adults having parental rights does not pose insuperable legal or policy issues. Prior contracts could be written in which the egg donor gives up parental claims, for a fee or out of altruism. Or, if two lesbians with healthy eggs use it to procreate with DNA from both women, they could get a prior contract written with the sperm donor to give up his parental claims.

Then all will be well unless separation or divorce occurs, when the courts will decide child support, custody and visitation rights in the child's best interests.

For example, in a US case, VC versus MJB (2000), made anonymous to protect the identities of the twins involved, a lesbian couple who had separated fought for custody.

One of the women had been impregnated with donor sperm and gave birth to the twins but both women had equally parented them. The New Jersey Supreme Court ruled that genetics was not determinative, so the gestational mother did not have priority: "Where there is a conflict over custody and visitation between the legal parent and a psychological parent, the standard to be applied is the best interests of the child."

Unless legislators write laws to regulate this and other reproductive technologies, courts will have to dispose with each case based on the specifics. While biology may matter, the courts are likely to adopt fluid understandings of parenthood in such domestic units and decide each case in the best interests of the child.

If Britain permits this "trigamous" technology, then its society will see these new family configurations soon enough. Since Singapore tends to adopt British life science practices, we might follow suit too. For us, there is a bright side: We could have more babies.


This article first appeared in The Straits Times on Oct 20.

Background story

If Britain permits this "trigamous" technology, then its society will see these new family configurations soon enough. Since Singapore tends to adopt British life science practices, we might follow suit too. For us, there is a bright side: We could have more babies.