A new egg screening technique has been used to help a 41-year old woman give birth to a baby boy after 13 failed attempts at IVF and three miscarriages.

The technique works by screening an egg before it is fertilised in order to check its chromosomes are healthy. An embryo with the wrong number of chromosomes has a higher chance of miscarrying or developing a serious medical condition such as Down syndrome.

The baby, Oliver was born in July. 'Oliver's birth is an important landmark in shaping our understanding of why many women fail to become pregnant', says Professor Simon Fishel, managing director of CARE fertility in Nottingham, UK, where the technology - called Array Comparative Genomic Hybridisation (Array CGH) - was developed.

Before an egg is fertilised it ejects half of its chromosomes to make way for the chromosomes provided by a sperm cell. In Array CGH, the ejected chromosomes are removed through a small incision made using a laser, and tested to make sure that each of the required 23 chromosomes have been left in the egg.

The major benefits of the technique are that eggs do not need to be frozen whilst they are being tested; the procedure can be carried out and results received in 48 hours. Moreover, the screening procedure reduces any harm done to the egg.

Experts such as Tony Rutherford, chairman of the British Fertility Society (BFS), have congratulated the Nottingham team, but warned that more research needs to be done before use of the technique becomes widespread. 'I would like to congratulate the team at CARE Fertility for their exciting research... and wish both mother and baby well. However, whilst the BFS supports the application of new technologies, it is essential that these new techniques are subject to further rigorous research', he said.

It is thought that Array CGH could double the success rates of IVF as defects in the egg are one of the main causes of miscarriage and failed fertilisation. 'Chromosomal abnormality plays a major part in the failure to establish a pregnancy. Up to half of the eggs in younger women and up to 75 per cent in women over 39 are chromosomally abnormal', says Professor Fishel. Of eight eggs screened from Oliver's mother, only two were found to be healthy. The technique costs approximately £1,950 in addition to the £3,000 to £6,000 cost of IVF, and is not currently available on the NHS.