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UK study finds men also have a biological clock

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  • Ian Pitchford
    FOR RELEASE: 1 AUGUST 2000 AT 01:00 ET US European Society for Human Reproduction and Embryology http://www.eshre.com/ UK study finds men also have a
    Message 1 of 1 , Jul 31 11:37 PM
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      FOR RELEASE: 1 AUGUST 2000 AT 01:00 ET US
      European Society for Human Reproduction and Embryology

      UK study finds men also have a biological clock

      The older a man is, the longer it is likely to take his partner to conceive
      irrespective of her age, according to research published today (Tuesday 1
      August) in Human Reproduction.*

      Women whose partners are five or more years older than themselves have less
      chance of conceiving in under a year of trying than women whose partners are
      the same age, or younger.

      The odds on conceiving in up to six months of trying decrease by 2% for every
      year that the man is over the age of 24, and for conception within 12 months
      decrease by 3% for every year.

      A decline in male fecundity (the likelihood of achieving a pregnancy within a
      defined period of time) has never before been confirmed or quantified by
      studies in the general population, so this research by teams at Bristol and
      Brunel universities** is the first to provide clear evidence that the age of
      the man, as well as the woman, is an important factor in conception.

      The conclusions have been drawn from data provided by the Avon Longitudinal
      Study of Pregnancy and Childhood (ALSPAC), known locally as the Children of the
      90s, which was designed to evaluate the effects of personal, social and
      environmental factors on the development of children from early pregnancy
      onwards. It had involved 85% of the pregnancies of couples living in the Avon
      Health Authority whose babies were due between 1 April 1991 and 31 December

      Over 8,500 of the couples who said their pregnancies were planned had stated
      the time taken to conceive: the Bristol and Brunel teams used these data to
      evaluate the effect of men's age on the time taken to achieve pregnancy.

      Miss Kate North, researcher in the Children of the 90s study, said: "It is
      really difficult to quantify the effect of men's age on fecundity because it is
      confounded by so many factors. But after adjusting carefully for all the
      variables we still found that women with older partners were significantly less
      likely than women with younger partners to conceive in under six or 12 months.
      Because of the size and composition of the study we are confident that our
      findings are robust and that the effect is real."

      The study concluded that in a couple who prove ultimately to be fertile, the
      probability that it will take more than 12 months to conceive nearly doubles
      from around 8% when the man is under 25 to around 15% when he is over 35.

      "It tells us that to some degree men as well as women have a biological clock
      that starts ticking as they get into their thirties and it also indicates that
      paternal age is another factor to be taken into account when doctors are
      looking at the prognosis for infertile couples," said Dr Chris Ford of the
      University Division of Obstetrics and Gynaecology at St Michael's Hospital,

      *Increasing paternal age is associated with delayed conception in a large
      population of fertile couples: evidence for declining fecundity in older men.
      Human Reproduction. W.C.L. Ford et al. Vol. 15. No 8. pp 1703-1708.
      ** Division of Obstetrics and Gynaecology and Division of Paediatric and
      Perinatal Epidemiology, University of Bristol,England; Brunel University
      Department of Health Studie, England.

      Full text of the paper with participating research teams can be found on
      website: http://www3.oup.co.uk/eshre/press-release/august.pdf
      Human Reproduction is a monthly journal of the European Society of Human
      Reproduction and Embryology.
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