The first large-scale study of genetic screening of embryos before implantation, published in January's issue of the journal Human Reproduction, has shown that the procedures used are safe for children born in single pregnancies.

The researchers compared 581 children who, as embryos, underwent preimplantation genetic diagnosis (PGD) or preimplantation genetic screening (PGS) with 2889 children conceived by intracytoplasmic sperm injection (ICSI) (with no PGD or PGS). The results showed that undergoing PGD/PGS did not affect the risk of preterm birth, abnormalities, death around the time of birth or low birth weight among children born in single pregnancies.

However, death rates around birth were significantly higher (11.73 per cent) for twins, triplets or other children born in multiple pregnancies than for single births (2.54 per cent). 'At present, we don't have an explanation for why the perinatal death rate should be so much higher in the PGD/PGS children, and we need to be careful about drawing firm conclusions from these observations as they may be biased due to low numbers', said Professor Inge Liebaers, head of the Centre for Medical Genetics at the University Hospital Brussels and a member of the Department of Embryology and Genetics at the Vrije Universiteit Brussels (VUB) and the leader of the Belgian research team. 'In addition, we were comparing them with the best possible group of ICSI children, and the demographic and medical backgrounds of the parents may have been different', she added, also calling for 'more careful, thorough and long-term follow-up studies after PGD'.

Professor Liebaers and her team studied children conceived using in vitro fertilisation (IVF) and ICSI at the same centre between 1992 and 2005. Questionnaires were sent to physicians and parents at conception and delivery. Children were examined at two months old by trained clinical geneticists, where possible. The health of children conceived using ICSI was studied so the team could ensure any health defects were due to PGD/PGS and not assisted reproductive technologies (ART) generally.

Professor Liebaers' study is 'as good as it gets' according to Joe Leigh Simpson, Professor of Human and Molecular Genetics and Professor of Obstetrics and Gynecology at the Wertheim College of Medicine, Florida International University, US, who wrote the editorial published alongside the research in Human Reproduction.