"There is a need for more careful, thorough and long-term follow-up studies after PGD, and the number of cases needs to be expanded. Just as for other forms of ART, not many centres have a well-structured follow-up programme. It is difficult to believe that this is the case since the most important outcome parameter is the health of the children born. The parents-to-be need to be fully informed on the health of offspring. Unfortunately, funding for these kind of studies is hard to find," said Prof Liebaers.

As pioneers in the field, the team at VUB has particular expertise in PGD/PGS and ICSI, and an accompanying editorial stresses the need for such expertise. Prof Liebaers said that to carry out PGD/PGS successfully, a close collaboration was required between a centre for medical genetics and a centre for reproductive medicine. Input was required from clinical geneticists and ART clinicians, embryologists, a genetics laboratory carrying out the diagnosis on a single cell, nurses, counsellors, psychologists and social workers.

"Only a close and smooth collaboration of all involved can provide the conditions for skilful practice of PGD. There are now several PGD centres, but only a few worldwide offering PGD for an ever increasing number of monogenic conditions."

The author of the editorial, Joe Leigh Simpson, Professor of Human and Molecular Genetics and Professor of Obstetrics and Gynecology at the Wertheim College of Medicine, Florida International University, USA, wrote: "PGD is not the purview of amateurs or the inexperienced, nor is any technical procedure. Inferential data suggest that less than fully experienced embryologists or diagnosticians may do more harm than good when performing PGD, especially PGD aneuploidy testing."

He concluded that Prof Liebaers study is "as good as it gets" and shows that: "In experienced hands, removal of one (or more) blastomeres does not result in an increase in birth defects. By extrapolation and analogous data, the same should apply to polar body or blastocyst biopsy. PGD is highly accurate (>99%). Whatever the controversy concerning efficacy of PGD in increasing pregnancy rates, patients may be informed that PGD is safe."