Vasectomies linked to genetic sperm damage

Dr Jess Buxton

Progress Educational Trust

24 June 2006

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[BioNews, London]

Vasectomies can cause chromosomal abnormalities in sperm, say a team based at Chulalongkorn University in Bangkok, Thailand. The researchers, who presented their findings at the annual conference of the European Society of Human Reproduction and Embryology (ESHRE) in Prague, Czech Republic, say that the genetic damage is caused by the original vasectomy, rather than reversal operations. The scientists say that men should consider freezing healthy sperm before they undergo the procedure.

Vasectomies work by obstructing the tube that carries sperm from the testis, thereby preventing sperm, which continues to be produced, from being ejaculated. Two years ago, researchers from Queen's University, Belfast showed that men who have undergone vasectomies and then had a reversal operation produce much less sperm than fertile men who have never had a vasectomy. The team also showed that the pregnancy success rate using intracytoplasmic sperm injection (ICSI) - a modified IVF treatment in which a single sperm is injected into an egg to fertilise it - was more than 50 per cent lower for the vasectomised men.

The new study confirms that vasectomies, even when successfully reversed, could affect sperm quality as well as quantity. The Thai researchers had been studying men affected by obstructive azoospermia, a condition in which sperm are created, but cannot be mixed with the ejaculatory fluid because of a blockage - as happens with a vasectomy. They found that these men had ten times the rate of chromosomal abnormalities such as aneuploidy (an abnormal number of chromosomes) and diploidy (two sets of chromosomes, rather than the usual one). These results prompted the team to investigate the rates of abnormality in ejaculated sperm after vasectomy reversal.

The scientists found that the longer a man had been rendered infertile by a vasectomy before having it reversed, the more chromosomally abnormal sperm he had. They also found that rate of abnormalities dropped with time after a reversal operation - that is, the longer ago the reversal, the better the chances of producing normal sperm. Team leader Professor Nares Sukchareon said that the study raised important questions, such as 'is the abnormal spermatogenesis [sperm production] reversible, and if so, how long will it take to get back to normal?'

Professor Sukchareon said that the findings may not affect babies born to men who have had vasectomy reversals, since the healthiest sperm might naturally be selected for fertilisation. But he added that until further research is carried out, 'it would probably be safer to freeze ejaculated sperm before vasectomy'. Dr Allan Pacey, senior lecturer in andrology at the UK's University of Sheffield, and spokesperson for the British Fertility Society, agreed, saying 'I think it would be a sensible insurance policy'.

Reproduced with permission from BioNews, an email and online sources of news, information and comment on assisted reproduction and genetics.