How does a sperm was affect motility?

I got the report of the sperm wash and prep from my two IUI attempts. On the first attempt, his initial motility was 49%, but the final motility was only 18% on a two day prep using two fresh samples collected 24 hours apart.   The total count was 21 million.  On the second attempt, his initial motility was 36% and the final motility was 19% with a total count of 10 million.  Does the sperm prep decrease the motility?  Has anyone had success at IUI with counts and motility this low?  His morphology is also poor, with increased tapered heads.

[babyprayers]

no the sperm prep for IUI, is done with a washing, then they add a special reagent to make motility quicker,

[thebabyproject]

If the prep is supposed to improve the motility, why was my DH final motility decreased from the initial?