After 35 reproductive clock ticks for men too

A new study by researchers in France has revealed that after the age of 35 men too experience a loss of fertility.

According to the researchers from the Eylau Centre for Assisted Reproduction in Paris, women's pregnancy rates drop and miscarriage rates increase when the father is over 35.

It is well documented that from around 35 a woman's chance of reproducing declines but this new research provides strong evidence that being an older father also poses a risk in terms of fertility.

The new findings are the result of research into 21,239 cases of intrauterine insemination (IUI) carried out in France involving more than 12,000 couples between January 2002 and December 2006.

IUI is a particularly effective type of artificial insemination where the sperm are 'washed', or spun in a centrifuge to separate them from the seminal fluid, and are then inserted directly into the uterus, if the sperm are not washed they can cause uterine cramps which can expel the semen because of prostaglandins in the seminal fluid.

In most cases the couples were being treated because of the husband's infertility and in all cases the husband's semen was used.

At the time of the IUI the sperm of each partner was examined for a number of characteristics, including sperm count, motility and morphology and clinical pregnancy, miscarriage and delivery rates were also carefully recorded.

A detailed analysis of the results allowed the scientists to separate out the male and female factors related to each pregnancy.

The research, while it confirmed as expected that women over 35 showed significantly decreased pregnancy rates, and higher rates of miscarriage compared to younger women, it also found that the age of the father was important in the rate of pregnancy.

Lead author of the study Dr. Stephanie Belloc, says for men over 35, there was a negative effect and even more surprising, the proportion of miscarriages also went up.

The researchers say although previous research has shown an overall decline in sperm count and quality as men age decade by decade, their study provides the first clinical proof that simply being an older man has a direct effect on a couple's fertility.

Dr. Belloc says they already believed that couples where the man was older took longer to conceive, but how DNA damage in older men translates into clinical practice has not been shown up to now.

Dr. Belloc says the research proves for the first time that there is a strong paternal age-related effect on IUI outcomes, and this information should be considered by both doctors and patients in assisted reproduction programmes.

Dr. Belloc says even though the numbers in the study were large, they intend to include more couples in the next few years to confirm their results further.

The research is published in the British journal Reproductive Biomedicine.