It definitely varies for everyone, that is for sure. I was denied short-term/long-term disability thru my employer's disability insurance carrier. I have just filed my second and final appeal. I applied for SSDI and was approved on the first try and within three months. I collected all of my medical records and supplied them to SSA, so I am sure that made it a little easier on them.
So sorry about your miscarriage and what you are going thru now.
Nanc