Short Cervix?

Shawnte

So I’m 21 wks and I had my anatomy scan today. The sonographer said my cervix was 2.5cm but is supposed to be 3cm. She said she wants me to come back in a week to keep a close eye on it. I don’t understand what this means and this is the first time I’ve heard of this. Can anybody help me understand why a short cervix is a concern?