Merle Spriggs argues that there are no good reasons to prevent a couple utilising preimplantation genetic diagnosis (PGD) when the sole aim of the procedure is that the resultant child is a compatible umbilical cord blood donor for a sick sibling.¹ I agree with much of the argument to support this, however, I believe Spriggs has omitted one important point and underplayed another.

The risk of PGD to the child born as a result of this process has not been fully studied. Therefore the parents are exposing the child to potential risks without benefit to that individual. This differs from the situation where PGD is done and a genetic disease is excluded as well as tissue matching. In this instance, the child benefits from being free of a genetic disease and also can act as a cord blood cell donor to his or her sibling.

What is known of the risks of PGD? PGD involves in vitro fertilisation (IVF) and intracytoplasmic sperm injection (ICSI) and much more is known about the risks to a child born as a result of IVF and ICSI. More than 4000 PGD cycles have been performed resulting in 1416 PGD embryo transfer cycles in Chicago plus 1670 transfers at other centres.² This has resulted in 338/1416 (23.9%) and 309/1670 (18.5%) clinical pregnancies and 539 children being born who are unaffected by the condition tested for. Importantly, multiple pregnancies occurred in about 33% of these. On the basis of these very small numbers there have been no deleterious effects attributable to PGD. IVF and ICSI have been studied extensively and a number of the negative outcomes exceed rates seen in naturally conceived pregnancies.³ These include risks associated with multiple pregnancies, prematurity, in utero growth retardation, and disorders of imprinting, particularly Beckwith–Wiedemann syndrome.⁴

An area I believe Spriggs has dismissed too lightly is “human dignity” and the assertion that “appeals to human dignity tend to be based in religion—not in reasoned argument”.¹ Suppose the sick sibling receives the umbilical cord cell transplant from the child born after PGD but dies despite this. In this situation it is conceivable that their family would mistreat the child who donated the cells as a result. It is possible that the child would be blamed for his or her sibling’s death. This is not a religious view of human dignity as suggested by Spriggs, but a view of possible parental psychological responses in an unusual situation.

At the end of the day, where a child will die without a haemopoietic stem cell transfer and no matched donor is available, my view is that the process outlined in the case of the Whitaker family¹ should be allowed to proceed. It is important, however, that the parents of the sick child contemplating PGD are aware of the potential risks to their planned offspring. It is also essential that they receive appropriate counselling to explore issues of the donor child’s place in their family.