Hi Carrie
Julie sent me an email about this here is my reply to her.

Your cervix is normally somewhere between 2.5 and 5cm long. A ‘short cervix’ can indicate that the baby will come early, however this is not always the case, in fact, the baby is often carried to full term. The problem is that we do not know which ones will come early and which ones will go to term. It is for this reason that the doctor will err on the side of caution.