Research carried out at the Centre for Reproductive Medicine in Shenyang, China, aimed to determine the effects of a short period of abstinence on the quality of ejaculated sperm, as well as its effect on the pregnancy outcomes of 500 couples undergoing IVF. Major molecular differences were seen between samples of semen depending on the duration of abstinence.
Specifically, semen samples collected after only one to three hours of abstinence contained more motile sperm with a higher reproductive potential than samples collected after men had abstained for three to seven days.
'For years, men have usually been advised to limit sexual activity to increase the chances of pregnancy. However, it’s time to change our minds,' said Dr Da Li, who led the study along with Dr XiuXia Wang.
'Our data indicates couples with relatively normal semen parameters should have frequent sex around the ovulation period. This could make all the difference to their efforts to start a family.'
Mass spectrometry used to analyse the protein content of semen showed that proteins involved in cell adhesion (important for fusing with the egg), motility and metabolism were increased when men abstained for only a few hours compared with days. The total antioxidant capacity of sperm was also significantly improved after reduced abstinence, leading to reduced genetic damage by oxidative stress and increasing the chance of viable proteins being formed.
Encouraging results were also seen in the couples undergoing IVF treatment. Typically, the live birth rate in a cohort of this size would be around 30 percent, said Dr Li. However, live births in the group using semen provided only a few hours after previous ejaculation were increased by one third compared with the group using semen ejaculated after a longer period of abstinence.
These results collectively suggest that having more frequent sex produces sperm of a better quality and increases the likelihood of a successful pregnancy.
The researchers now plan to carry out further research into the protein composition of semen, specifically looking at the post-translational modifications of the different samples. The Centre for Reproductive Medicine is also updating its IVF protocols to use semen from shorter periods of abstinence.
The study was published in Molecular and Cellular Proteomics.