“Why should we offer screening for Down syndrome anyway?”

Abstract

The details of a surrogacy case involving an Australian couple commissioning a pregnancy in Thailand have created outrage in all sorts of quarters. But the father’s admission that he would have asked the surrogate mother to terminate her pregnancy if he’d known baby Gammy had Down syndrome didn’t cause indignation in anywhere the same scale. The notion of disability – and how we value or devalue people with it – makes many uncomfortable. Nevertheless, the screening most pregnant women choose to determine whether their child will have Down syndrome, and the terminations that result from it, are widely practised. At around 12 weeks gestation, a woman may elect to have a combined screening test involving an ultrasound and a blood test. The results from these investigations provide a probability of the fetus having one of a few chromosomal trisomy conditions. These conditions result from having three copies of a chromosome, rather than the usual two. They can be lethal in utero or lead to a very short life (such as with trisomy 18, known as Edwards syndrome and trisomy 13, known as Patau syndrome), or a spectrum of mild to significant intellectual disability, often presenting with cardiac problems (trisomy 21 - Down syndrome). Based on this probabilistic information, the woman can then decide whether she would like to obtain further, and likely more accurate, information. At the moment, this usually involves invasively obtaining a sample from the placenta or amniotic fluid. Some women decide to have this, some do not. And some will be informed that their fetus will be born with a chromosomal trisomy. Of these, most will terminate. We don’t know how many women do this in Australia as data is not kept in a consistent way between states. But in the United Kingdom, a 2009 paper gave the termination rate for detected cases of Down syndrome as 92%. The ethical question is whether such screening, and ending those pregnancies where a condition is identified, is acceptable.