Foetal genome sequencing

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Last Summer, researchers led by Jacob Kitzman at the University of Washington sequenced the entire genome of a human foetus, triggering one of the most emotionally loaded debates of the year. The results promise a single non-invasive test to diagnose a broad range of genetic diseases as early as eight weeks into a pregnancy.

At the moment, expectant parents in an at-risk group can opt into amniocentesis or chorionic villus sampling; invasive tests that involve inserting a long needle through the abdomen, with a small risk of miscarriage. So why is the debate so loaded? Because despite the various reasons why pregnant women take the test, around 85% decide to abort if told they will have a child with disabilities.

Kitzman’s team isolated the 10% of DNA in a mother’s blood plasma that is her baby’s, using a DNA sample from the father’s saliva for comparison. The benefits of the new technique are threefold. Firstly, it does not entail the risk of miscarriage, which appears enormous to many expectant parents. Secondly, diagnoses could be made earlier in the pregnancy. Finally, this approach may be more reliable than the current tests, which throw up a significant number of misdiagnoses.

However, it is the one-time nature of the test that raises some doctors’ concerns, specifically that it might mean poor quality advice for the parents. One NHS clinician described to me how she frequently pacifies frantic parents who have had news delivered from scan-performing experts, rather than condition-diagnosing experts, requiring her to dispel an image of their child who they think may never achieve psychological normality. Our current system continuously refines the high-risk category — mothers over 35, those with a family history of genetic illness, pregnancies with a backdrop of problematic fecundity — providing layers of preparation for parents. But this could be peeled away by a one-test system. Proper counselling should involve more than a half-hour chat before the test, and provisions must be made to prepare the parents for a very difficult decision.

The American presidential election brought the issue of prenatal testing into the limelight. The Republican nominee Rick Santorum, who has a daughter with Edwards syndrome, attacked the Affordable Care Act’s free testing policy as a “search and destroy mission” to “cull the ranks of the disabled in our society”. There is widespread and strong opinion that the availability of such testing contributes to, or even stems from, bad feelings towards the disabled in society. But there are opposing views even from within the American right. Sarah Palin was “grateful for all those months to prepare” for her son with Down’s syndrome, and there are likely to be families who need the time to get together money and medical expertise. In a discussion on the popular parenting website Mumsnet, another woman spoke about her first child, who was born with a rare disorder that led to a short life full of pain. She told me it was not until she was pregnant with her second child that doctors realised the condition was genetic. She had an amniocentesis that identified a healthy foetus, and avoided a pregnancy filled with misgivings.

A rule of thumb is that the earlier the (invasive) test, the bigger the risk of miscarriage (3.5% of pregnancies are lost at 10 weeks; 0.3% at 20 weeks). Naturally then, many parents leave the decision as late as 20 weeks into the pregnancy, by which point their baby has grown hair, unique fingerprints and nails. The new, non-invasive tests would eliminate this risk — which mainly arises from amniotic fluid loss — meaning parents could choose when to test based solely on the potential outcome. This may seem inconsequential if the screen is only for preparation, but for those who might terminate the pregnancy based on the outcome, it is pivotal. Some religions make the choice clear. Despite the strong anti-abortion stance of Islam, Shï’a law posits that ‘ensoulment’ occurs up to 17 weeks into pregnancy, and abortion in dire need is permissible up to four months, so concerned Muslim parents need information as soon as possible. This hazily follows the dominant secular school of thought, which assigns a lower moral status to younger foetuses, perhaps making a later decision more difficult even for pro-choice parents. Interestingly though, a significant minority of Mumsnet denizens were concerned that having to make a decision so soon did not give mothers enough time to bond with their quickly growing child.

Hopefully these screening developments will go hand-in-hand with developments in treatment, such as in utero surgeries for spina bifida, allowing more pregnancies to result in the birth of a healthy child. For this, the zoomed-in resolution of the complete-genome tests can only help. It might even eradicate stories like that of a mother who had received a positive result for Down’s syndrome, and spent the last three months of her pregnancy grieving the loss of the healthy child she had always imagined. She and her partner had prepared themselves as well as they could, even moving nearer a better-equipped hospital. Their daughter was born without the condition, and they were left to reconcile themselves with their choices.

Another facet of better diagnostic resolution is being able to spot less debilitating or later-onset diseases, making selective abortion for less detrimental disabilities a concern. This leads the debate to eugenics, as seems inevitable for every discussion of prenatal testing. If the genome of a foetus is available to the parents, termination decisions could theoretically be made on gender, paternity, and perhaps one day, sexuality. There is also talk of parents who are deaf preferentially aborting foetuses who are not, and ‘screening-in’ disabilities. It all leads us to the question, what is the moral authority of Nature these days? As our dominion over the natural order increases, has the debate caught up with it? And do we have the right to the child we want?

ILLUSTRATION: Tristan Varela

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