Editorial: Take care with embryo trial

It is a civilised world that intrudes with extreme care on the natural selection of human beings.

It would have been easy now for a clinic such as Fertility Associates of Auckland to have quietly begun screening embryos for likelihood of survival and replacing those that did not measure up. It has the technology, a device that can sense whether the right number of chromosomes are present in a cell, and it is in trial use for checks on placentas. If the technique can be performed on an embryo cell, the prospects of a successful pregnancy can be detected early.

The benefits for those on in vitro fertilisation programmes, particularly older women, are obvious. But so are the more controversial possibilities. The technique, fluorescent in situ hybridisation, "Fish" as it is perhaps unfortunately known, can do more than count chromosomes. It can assess whether they are abnormal, detect the sex of the embryo and screen for disorders such as Down's syndrome.

Fertility Associates has received permission to use the technique only to check the viability of embryos fertilised by its in vitro process and only for a trial. After that, the clinic will need to reapply to the Ministry of Health's national ethics committee for the right to use the process routinely. Clearly the doctors and the ethical guardians are proceeding with due care.

Just as clearly, there will be concern in some quarters that embryonic life may be aborted when it fails the Fish test, so to speak. But in vitro fertilisation already involves the cultivation of more than one embryo and a selection is made before implantation. If abnormalities are to be a reason for termination it is better decided at the embryo stage than as a consequence of an amniocentesis at 15 weeks.

But nature remains a far more selective arbiter of embryonic survival than science threatens to be. This technique offers greater prospect of success to those struggling to bear a baby. There is a line to be drawn but it is some way off yet.