Fatherhood may already be moving out of reach for men in their mid-thirties, a new study suggests. Infertility doctors found that miscarriage rates increased significantly when the prospective father was older than 35.
John von Radowitz
Fatherhood may already be moving out of reach for men in their mid-thirties, a new study suggests.
Infertility doctors found that miscarriage rates increased significantly when the prospective father was older than 35, while pregnancy rates dropped after the age of 40.
It is the first time paternal age has been seen to have such a strong effect on reproductive success.
Although the study involved thousands of men and women being treated for infertility, its findings are relevant to all couples, say the researchers.
Study leader Dr Stephanie Belloc, from the Eylau Centre for Assisted Reproduction in Paris, said: "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 the gynaecologists must also focus on paternal age and give this information to the couple."
Dr Belloc's team followed up a total of 21,239 artificial insemination procedures carried out between January 2002 and December 2006.
The 12,236 couples had decided to try intra-uterine insemination (IUI) after having difficulty conceiving. IUI involves spinning sperm in a centrifuge to separate it from seminal fluid and then inserting it directly into the womb.
Artificial insemination can involve the use of donors but every male participant in the study was a husband.
Before each procedure, researchers noted the quantity, activity and shape of the man's sperm.
Pregnancy, miscarriage and delivery rates were also recorded. Detailed analysis allowed the scientists to separate out male and female factors relating to pregnancy success or failure.
As expected, pregnancy rate was significantly reduced for women over the age of 35.
But the study unexpectedly found that being older than 35 also made it harder for men to become fathers.
For men aged 34, the miscarriage rate was 16.7%. But between 35 and 39 it rose to 19.5%, with almost one in five pregnancies ending in miscarriage. By the age of 44 it had reached 32.4%.
Pregnancy rates only began to change significantly when husbands reached the age of 40. As men's age increased from 39 to 44 the proportion of treatment cycles producing a pregnancy fell from 13.4% to 10.9%.
The findings are presented today at the annual meeting of the European Society of Human Reproduction and Embryology (ESHRE) in Barcelona, Spain.
While the effect of a woman's age on her ability to conceive is well known, there is controversy about the impact of age in men.
Many reports show an overall decline in sperm count and quality as men age, but experts have disagreed on whether or not this is simply the result of getting older.
Lifestyle factors such as smoking and obesity have also been blamed for reduced fertility in older men.
"We already believed that couples where the man was older took longer to conceive," said Dr Belloc. "But a number of reasons had been put forward for this. Neither was there any definite evidence that miscarriage rates increased when the man was older.
"Some recent studies have established a relationship between the results of IUI and DNA damage, which is also correlated to a man's age, suggesting that it might be an important factor, but until now there was no clinical proof.
"Our research proves for the first time that there is a strong paternal age-related effect on IUI outcomes."
She added that the findings were not only relevant to assisted conception patients but had "important implications" for all couples wanting to start a family.
