Timing is key to fathering children
New research suggests men's biological clocks are also ticking
FERTILITY EXPERTS have warned there is a growing body of evidence showing that the man's age is a significant factor affecting the chances of a couple conceiving and of having a healthy child.
A new study presented last week at the annual meeting of the European Society of Human Reproduction and Embryology in Barcelona found that miscarriage rates increased significantly when the man was older than 35, and that pregnancy rates dropped when the man was older than 40. The study was based on more than 12,000 couples attending a fertility clinic in Paris.
Professor of reproductive medicine at Queen's University Belfast, Sheena Lewis, who also presented a paper at the conference, said the Paris study "provided more data to add to an emerging picture" relating to the significance of the age of the father.
She said people needed to realise that they are taking a risk by waiting until they were 35 years or older to have children - as an increasing number of women and men are. "You cannot assume that it will happen, that it will not be a problem," she said.
Prof Lewis, who is a scientist at the Regional Fertility Centre at the Royal Victoria Hospital in Belfast, said there was a growing trend of people leaving it later to have children when their careers were established, and of people trying to start second families later in life. She said the clinic was seeing an increasing number of men in their 40s and 50s who wanted to have children, often in a second relationship.
People often mistakenly assume they will be able to have children later in life, she said. "What happens is that we are inclined to take anecdotal evidence and assume that it applies to the whole population - so people hear about Cherie Blair and Madonna having babies and assume that older mothers can have easy pregnancies.
"And they hear about Picasso fathering a child when he was 81, and they believe that every man can do it, and it becomes the accepted wisdom, but unfortunately it is not the case. We are perpetuating a myth and people often believe it until it is too late," Prof Lewis said.
She said there were now quite a number of studies showing that as a man ages, the likelihood of his sperm being damaged increases. "A sperm is a very specialised little cell - it is just DNA with a tail and it has one single function, to get the DNA to the egg to fertilise it. In order to do that, the cell gets rid of everything but DNA, so it gets rid of repair mechanisms that you find in other cells. So if it gets damaged it can't repair itself."
She said that after fertilisation, the DNA damage of the sperm becomes part of the genetic make-up of the embryo. "If a poor sperm fertilises an egg, and even if you get a pregnancy, there is quite often a miscarriage," Prof Lewis said. While one study had suggested that an egg could repair a damaged sperm, she said there was not a great deal of evidence to support this, and further research would be needed to test it. She said other studies had shown that when a man is older it takes longer for a couple to conceive.
Dr Stephanie Belloc, who led the study at the Eylau Centre for Assisted Reproduction in Paris, told the Barcelona conference: "Until now gynaecologists only focused on maternal age and the message was to get pregnant before the age of 35 or 38, because afterwards it would be difficult. But now gynaecologists must also focus on paternal age and give this information to the couple."
The study examined 12,236 couples who had decided to try intra-uterine insemination (IUI) after having difficulty conceiving. This procedure involves spinning sperm in a centrifuge to separate it from seminal fluid and then inserting it directly into the womb.
Pregnancy, miscarriage and delivery rates were recorded as were the quality, activity and shape of the men's sperm. The analysis separated out male and female factors.
As expected, women over the age of 35 were less likely to get pregnant but the man's age was also found to be a significant factor both in miscarriage rates and pregnancy rates.
For men aged 34, the miscarriage rate was 16.7 per cent, but for men aged between 35 and 39 it rose to 19.5 per cent, and by age 44 it had reached 32.4 per cent.
Pregnancy rates only began to change significantly when the men reached the age of 40. As the men's age rose from 39 to 44 the proportion of treatment cycles producing a pregnancy fell from 13.4 per cent to 10.9 per cent.
Dr Belloc said the study "proves for the first time that there is a strong paternal age-related effect on IUI outcomes" and she said the findings were relevant to all couples wishing to have children.
Prof Lewis and her colleagues in Belfast are currently conducting research into "lifestyle hazards" that affect male fertility. These include smoking, alcohol, sexually transmitted diseases, recreational drugs and substances that mimic oestrogens which are found in some products ranging from certain foods, aerosols and body creams, and plastic food coverings. Much of the research in this area was prompted by a Danish finding in 1992 that men's sperm count had declined by 50 per cent in 50 years.
Prof Lewis said a recent study in Denmark had also found that 40 per cent of young men had a low sperm count. "It appears to be a particular problem in northern Europe," she said.
The paper she presented at last week's Barcelona conference concerned the impact of cannabis use on male fertility. The study found that cannabis use decreased sperm motility - the pace at which sperm can swim. Other studies have also shown that cannabis use reduces sperm production.
She said that men who wanted to become fathers should be aware that it takes about 70 days for a sperm to be produced, so the "lifestyle hazards" such as smoking and recreational drugs should be avoided for at least three months if they want their sperm to be healthy.
She also pointed out that studies suggest that a father smoking, and the resulting damage to the sperm DNA, can lead to an increase in certain childhood illnesses, in particular some forms of cancer and more recently an association has been found with autism.
"When a mother smokes and damages the egg, the egg has the capacity to repair the damage, but the damage to the sperm becomes part of the embryo's genetic make-up," she said.