New research has found that pregnancy rates decrease and miscarriage rates increase when a father is over 40 years of age. According to French scientists, this is the first time that such a strong paternal effect on reproductive outcomes has been shown.
They looked at over 21,000 IUI cases. IUI (intrauterine insemination) is a type of fertility treatment in which the sperm is specifically treated and then inserted directly into the uterus.
Altogether, more than 12,000 couples were involved in the study over a five-year period. In most cases, the couples were being treated because of the husband’s infertility.
The sperm of every man was examined at the time of each IUI for a number of characteristics, including sperm count and motility (the ability to move). Pregnancy, miscarriage and delivery rates were carefully recorded and a detailed analysis of the results allowed the researchers to determine the male and female factors related to each pregnancy.
Not surprisingly, maternal age was found to be closely linked with a decreased pregnancy rate and a higher miscarriage rate.
“But we also found that the age of the father was important in pregnancy rates – men over 40 had a negative effect. And perhaps more surprisingly, miscarriage rates increased when the father was over 40,” explained Dr Stephanie Belloc of the Eylau Centre for Assisted Reproduction in Paris.
The researchers noted that while maternal age has long been linked to the ability to conceive and miscarriage rates, there is still controversy over the role of the father. While studies suggest an overall decline in sperm counts and quality from decade to decade, until now, there has been no clinical proof that simply being an older man has a direct effect on a couple’s fertility.
“We already believed that couples where the man was older took longer to conceive, 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…This research has important implications for couples wanting to start a family,” Dr Belloc said.
While the number of people involved in this study is already large, the researchers intend to include more couples in the next few years to further confirm their results.
Details of these findings were presented at the 24th annual conference of the European Society of Human Reproduction and Embryology.
