Robert Winston's attack on IVF clinics for exploiting patients for profit "out of their desperation to get pregnant", and by offering tests for which "there was no clinical justification" is unwarranted, misleading and a disservice to patients (Winston: IVF clinics corrupt and greedy, May 31).

Lord Winston was particularly critical about a test for chromosome screening which "costs several thousands of pounds, [and] is routinely used to weed out unviable embryos", adding that "most of the people who are doing this work are doing a form of cookery without understanding the science behind it".

Abnormalities in the number of chromosomes an embryo inherits at fertilisation are the main cause of pregnancy failure. In IVF treatment, screening embryos before they are returned to the uterus is a well established method for identifying these abnormalities. Our own patients are always informed of the limitations of the test. Yes, we can only "interrogate a tiny portion of an embryo's genome", but there is no assertion that we are doing otherwise.

Contrary to Lord Winston's claim that the Human Fertilisation and Embryology Authority has "not prevented the exploitation of women" nor "limited the number of unscientific treatments people have access to", this and other similar tests on embryos are tightly regulated.

The incidence of eggs and embryos with abnormal numbers of chromosomes increases dramatically in women in their late 30s and 40s and, even for the limited number we can detect, averages 40% in this age group and in some cases can affect all embryos. The result of the testing is safer IVF. It would be irresponsible not to offer this screening to high-risk patients.

We agree that the cost of this screening is high. Lord Winston has himself published on these specialised and difficult tests, which require not only expensive probes and equipment but also a multidisciplinary team. Paradoxically, however, screening is fairer to women whose embryos can be identified as non-viable - significantly reducing the cost and risk of failed cycles, and the associated emotional implications.

Lord Winston is right in one respect. Ongoing research will improve our screening and diagnostic abilities, and in time it will be possible to screen for all 23 pairs of chromosomes while at the same time reducing the cost of this highly detailed, highly skilled process.

Lord Winston returned thousands of untested embryos during his work as a fertility specialist at Hammersmith hospital without the benefits of this vital knowledge. He was supportive of the early development of preimplantation genetic diagnosis and screening, but we believe he has now misjudged its significance.

Our commitment as a fertility centre is to patient care and continued research. Safer IVF and the avoidance of disability, wherever and whenever possible, is our primary objective. It is regrettable that Lord Winston has lost sight of this in his rush to criticise.

· Professor Alan Handyside is the director of the London Bridge Fertility, Gynaecology and Genetics Centre
ahandyside@thebridgecentre.co.uk