Hi Chrissy

Your cervix is part of your uterus and is normally about 4cm long. Try to imagine a balloon. The balloon itself is the uterus and the part that you blow into is the cervix. When your uterus starts to contract it actually starts to pull up the cervix and in doing so causes it to become shorter. So if your cervix is shorter it is an indication that your uterus has been contracting. These early contractions can be very mild and some women may not even realise that they are contracting.

Hope this answers your question.