Women's fertility starts to deteriorate when they hit their mid-thirties. Past studies suggested sperm quality also begins to decline in men above 35, which could possible impact fertility.

Newcastle Fertility Centre at Life in the UK conducted a study, which used sperm donations to evaluate sperm quality. The aim of the study was to show that men in their late thirties do not produce low quality sperm, but that sperm from men in their forties had a more effective chance of turning into a successful pregnancy.

The researches noted this is an early research explaining that young men who are sperm donors may not know if they are fertile or not.

About 230,000 sperm donations that were registered by the Human Fertilisation and Embryology Authority between 1991 and 2012 were analyzed using in vitro fertilization or the technique of donor insemination.

The study showed that age had an impact on the fertility of the women. About 29 percent live birth rates from in vitro fertilization with donated sperm in women between the ages 18 and 34 were observed in comparison to 14 percent success rate in the plus-37 group.

The sperm donors were split into six age groups: under 20, 21 to 25, 26 to 30, 31 to 35, 36 to 40, and 41 to 45. It was observed that age had no impact in the results. The results showed young women had a 30.4 percent success rate when given sperm from donors between ages 41 and 45 as opposed to 28.3 percent live birth rates in women who were given sperms from donors below aged 20.

Dr. Meenakshi Choudhary, reproductive endicrinologist, said, "Despite these trends, it's important to note that the impact of sperm donor age on live birth failed to reach statistical significance in any of the age groups we studied. Indeed, this trend of less likelihood of live birth with younger sperm donor age might simply be explained by the fact that younger men who donate sperm are less likely to have proven fertility themselves than older sperm donors with proven fertility."