The first thing a woman seeking to conceive via fertility treatment will undoubtedly be told is the impact her age will have on her chances of a successful pregnancy.
But now a study of nearly 19,000 IVF cycles has shown how the influence of the paternal age on live birth rates could play a more vital role than previously thought.
It found that for women under 35 or over 40, the age of their male partner made little difference to their chances of giving birth. But for women between the ages of 35 and 40, there was a “significant drop” in the live birth rate if the male partner was aged 40 and above.
The results challenge widely held assumptions that maternal age should always be the primary consideration, and they could help shape fertility education and messaging for couples trying to conceive.
“The findings add to a growing body of evidence which shows fertility is very much a male issue too,” said Kate Brian, operations manager at Fertility Network UK.
“Our increasing awareness of the influence of male fertility highlights the need to ensure fertility education both for school-age children and couples planning a family.”
Professor Geeta Nargund, one of four authors who contributed to the study, said: “For too long the burden has been on women, and the man’s contribution for the short- and long-term risks to the offspring associated with advanced paternal age have been largely ignored.”
Nargund, medical director of Create Fertility and consultant gynaecologist at St George’s Hospital in Tooting, south London, added: “Clearly it is very important that we do not ignore the paternal age when it comes to educating couples about fertility treatment outcomes. A woman’s age obviously plays a large role but not all the focus should be on her biological clock.”
The retrospective clinical study is based on anonymised data from the UK fertility regulator, the Human Fertilisation and Embryology Authority. It analysed the interaction of the maternal and paternal age in 18,825 IVF and ICSI (where the sperm is injected directly into the egg to aid fertilisation) cycles following a single fresh embryo transfer.
It showed that when women were under the age of 35, said Nargund, “laboratory results indicate that the eggs from younger females have the capacity to repair the much higher incidence of DNA damage found in the sperm of older males”. When a woman is older than 40, egg quality is lower and the egg is less capable of repairing any damage found in the sperm.
“However, what is really interesting is the man’s age seems to have more impact when the woman is between 35 and 40,” Nargund said. The live birth rate drops from 32.8% where the paternal age is under 35 to 27.9% where the paternal age is between 40 and 44. Where the male partners were over 55 years old, the live birth rate was 25%.
Nargund said: “We know an older paternal age delays conception, reduces the fertilisation rate and can lead to increased miscarriages or mental health disorders in the offspring. But now we know that, for women in a certain age bracket, that paternal age is more significant than previously thought when it comes to live birth rates.”
Nargund says the interaction between the ageing egg and sperm at the time of conception is more complex than previously thought, and the potential ability of both egg and sperm to “repair the effects of the ageing process” needs to be better understood.
