AM or PM: is there a difference in semen quality collected at different times during the day?

This study investigated if the time of collection (ToC) affects semen parameters in men with infertility. 

They found that motile sperm count (sperm that move normally; MSC) was higher in semen collected in the evening than in the morning. 

Male infertility (MI) affects roughly half of infertile couples. There can be many causes of MI. Semen analysis is used to diagnose MI. Semen parameters can tell us what is causing infertility. Sperm count (SC) or concentration (SCC) indicate how many sperm are present. Sperm motility (SM) and morphology (shape; SMP) indicate how well the sperm can function. 

Semen collection is the first step to treat couples with MI. Sperm can then be used for in vitro fertilization (IVF). It can also be delivered directly into the uterus. This is called intrauterine insemination (IUI). Sperm collection is performed early in the morning in most fertility clinics. There is some evidence that sperm parameters are different when the collection is done in the morning or evening. It is unclear if the time of collection (ToC) affects sperm parameters. 

This study included 40 men. 20 men had normal fertility. 20 men had abnormal sperm parameters. Semen collection was performed at 7 a.m. on one day. Semen was collected at 5 p.m. on another day. The main sperm parameter evaluated was motile sperm count (MSC). 

MSC was higher in semen collected in the evening. This was observed in both fertile and infertile men.  Semen volume, sperm concentration, and motility were also higher in the evening compared to morning samples.

The authors concluded that MSC was higher in semen collected in the evening. The authors suggested that better IUI results might be achieved if evening semen samples were used.

The number of men in this study. Other factors could also affect sperm parameters. It is unclear if the ToC is associated with better fertility outcomes e.g. pregnancy rates. Larger controlled studies are needed.

If you have any concerns regarding infertility please consult with your physician.