For the study, timelapse video footage of 3,532 embryos taken from 527 couples was examined.
Those created with sperm from men over 50 developed 35 per cent more slowly than embryos created with sperm from men under 35.
Considering only embryos that reached the blastocyst stage, the time to reach this point was 4.3 per cent slower for the embryos of men over 50 than for the embryos of men under 35.
In a further study, researchers from Weill Cornell Medicine in New York showed that as men age, their sperm becomes more prone to develop mutations that result in DNA errors.
Sperm from older men was found to have an abnormal number of chromosomes in each cell – either too many or too few, a condition called aneuploidy. This will make the sperm less likely to create a healthy embryo.
The team analysed the DNA of sperm from men whose partners were experiencing recurring pregnancy loss.
The men were divided into seven age groups, with the youngest group aged 25 to 30 and the oldest over 55. Their sperm was tested for aneuploidy and DNA sequencing for a type of mutation called CNV or ‘copy number variation’.
Both types of defects were highest in the oldest age group. Fertilisation rate was 87.7 per cent in the youngest age group and declined to 46 per cent in the oldest group.
American Society for Reproductive Medicine vice-president Peter Schlegel said: ‘These studies make it clear that for men as well as women it may be difficult to have a child at an advanced age.
‘Older men and their partners should be counseled about the risks of poor pregnancy outcomes and the potential for neurodevelopmental problems in offspring.’
