Does a low sperm count on the day of IUI affect pregnancy rates?

This study assessed whether males with normal sperm but poor sperm motility on the day of insemination had higher pregnancy rates than males with diagnosed infertility. The study concluded that even if sperm motility was low on the date of insemination, males who previously had normal sperm had better pregnancy rates.

Male infertility is the inability to reproduce naturally. Defective sperm function is the most common cause of male infertility. Sperm motility (the sperms' ability to swim) is an important predictor of pregnancy.

The success of intrauterine insemnination (IUI, a fertility treatment where fast moving sperm are placed into the woman's womb close to the time when the egg is released from the ovary in the middle of the monthly cycle) depends on the quality and quantity of sperm. It has been observed that some males with normal sperm in the 6 months prior to treatment had poor sperm motility at the time of IUI. The significance of a poor total motile sperm count (TMSC) on the day of insemination in these males is unclear. 

This study aimed to determine if males with low TMSC on the day of IUI performed as poorly as those who had known infertility prior to commencing treatment.

147 males with abnormal sperm analysis underwent 356 cycles of IUI with controlled ovarian hyper-stimulation (a technique to induce ovulation in females). Their pregnancy rates were compared with 120 males (265 cycles of IUI) with normal sperm but poor TMSC on the day of IUI.

Pregnancy rates were much higher in the group with low TMSC on the day of IUI (17%), compared to the group with known infertility issues (5%).

The study concluded that males with normal sperm analysis, but low TMSC on the day of IUI, performed better than males with known infertility. 

This was a small, retrospective study.

If you are underoing IUI, these results may be relevant to you and worth discussing with your physician.