All in the head?
Dr Kirsty Horsey
Progress Educational Trust
15 November 2001
A study has shown that current standards used as indicators of male infertility may be wrong, meaning that some men may have been inaccurately diagnosed. US scientists have suggested new thresholds for sperm counts and motility analysis that currently distinguish fertile and infertile men. The new thresholds would both raise the standard for fertility and lower it for infertility. The current thresholds, widely used by doctors, were set by the World Health Organisation (WHO). Semen has been classified as normal if it contains at least 20 million sperm per millilitre and at least half of them are motile. The criteria for the number of well-shaped sperm that must be present is not accurately estimated in the WHO guidelines; nor do they make it clear what the 'cut-off points' for fertility and sterility are.
The new study, published in the New England Journal of Medicine, suggests that well-shaped sperm is the best indicator of male fertility. Dr David Guzick, of the Rochester University Medical Centre in New York, led a team of doctors from seven other universities. They studied the semen of 765 men from so-called infertile couples and of 696 men from couples who had had children.
The study showed that men were most likely to be fertile if their semen had more than 48 million sperm per millilitre, if more than 63 per cent of the sperm were motile, and if more than 12 per cent of the sperm were well-shaped. Men were more likely to be regarded as infertile if they had fewer than 13.5 million sperm per millilitre, less than 32 per cent motility and fewer than nine per cent were well-shaped. Anything between these values was classified as 'indeterminate' fertility. A well-shaped sperm was described as having, among other things, 'an oval head and whippy tail'.
© Copyright Progress Educational Trust
Reproduced with permission from BioNews, an email and online sources of news, information and comment on assisted reproduction and genetics.
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