Question: how many cm do you have to be dilated for your water to break?
Answer: If your cervix has opened up to at least 2-3 centimetres dilated and the baby's head is well engaged (low down in your pelvis), your waters will be broken (see below under Artifical Rupture of Membranes). If it is not possible to break your waters a second Propess pessary may be inserted if appropriate.