I had a miscarriage 2 days ago. i was asked to do a pelvic scan. it was discovered that i have an anterior intramural uterine fibroid of 20mm 18mm . could that be the cause of the miscarriage? and can it pose a threat in future pregnancy?

Yes and maybe: Intramural fibroids usually impact pregnancies in the third trimester when the uterine expansion is competing with the developing fetus. Sub-mucous fibroids (under the lining of the womb) can cause 1st trimester miscarriages. Future pregnancies with your intra-mural fibroid are a 50/50 proposition if it greatly enlarges. Myomectomy is an option in that case.(Fibroid removal saving the uterus)

Possibly: , but more likely not. Fibroids are very common, and relatively small as in this case. Submucosal, or intracavitary are more troublesome regarding pregnancy retention.