Are the chances of a successful iui higher when the sperm count is very good?

Yes: Success rates are better with normal sperm counts. However, most studies suggest that once you have over 10-20 million moving sperm in the IUI specimen then the pregnancy rates are the same. Counts of <1 million sperm are much less likely to result in pregnancy. Counts of > 1million and < 5 million can lead to pregnancy but again higher is better. My record low count was 50, 000 for an IUI baby.