Does trichomoniasis cause infertility?

Yes. Trich causes inflammation in the cervix, which blocks the cervix and reduces sperm available to the egg. Trich is commonly associated with other gynecologic illnesses, like chlamydia, which can inflame and damage the fallopian tubes. Women with trich and other pelvic infections should seek medical care right away.
Rare cause ... Trichomonas (tv) is more common in infertile women in some studies. In women tv may cause tubal infertility by causing pelvic inflammatory disease, possibly by allowing other std's to cause damage. It may just be a marker of increased risk of stds like chlamydia. In men, it is a rare cause of infertility, but tv may directly reduce sperm motility. It may infect epididymis, even testicles: orchitis.