I think at some point I read around 25% of women who take clomid have this as a side effect. Aside from clomid, I don't know what causes it, but with IUI you can over come that problem.
Best of luck to you..
Cervical mucus is described as "hostile" when it is too thick to allow sperm to penetrate the cervix, thereby preventing conception.
Women who are taking Clomid to induce ovulation frequently experience hostile mucus.