starting progesterone at 23 weeks?

Ap
Ok, so this is definitely not my first rodeo. I have had extremely easy non complicated pregnancies . I have had 5 children first two natural , then twins and a singleton via surrogacy c-section. I am used to progesterone shots in the rear due to surrogacy but I have NEVER heard of starting progesterone at 23 weeks - my last baby was born 36,3 and they said it is to prevent preterm labor? Anyone experience this or have done this? I'm not crazy hopeful as I have been blessed so far but planning for a complication to arise, not to mention I feel like absolute 💩 this pregnancy, cramping back pain all things I've never experienced until last few weeks.