Endocervical Polyp during pregnancy.

Hello, in my NT scan they discovered a Echogenic lesion which they they think is a polyp measuring 1.2cm x 0.3cm in the upper part of my cervix. Internal os is closed. I also have a cervical cerclage + pessary placed due to my previous history of miscarriage at 17 weeks due to incompetent cervix. I'm currently 15 weeks pregnant, my doctor said they won't remove the polyp now as its in the upper part and since it's risky to remove it now, at 14 weeks i had another scan in which it showed the polyp is measuring 1.5cm x 0.5cm and my cervix length is already short at 2.8cm. It hasn't caused any issues like bleeding so far. But I have increased discharge which is yellow in colour. Doctor said the polyp could be causing it. Also, My lower part of placenta is only 1.3cm away from my internal os My question is what has caused this polyp and is it dangerous to leave it alone? Will it cause any trouble to my cervix as it's already incompetent? Will the placenta move away from the cervix?