I've always been curious about how wide a baby goat is when it's born and how wide the doe's pelvis has to be in order to pass the baby. Anyone have any input? (You can use cm or inches to talk about the measurements)
There really isn't an answer to your questions. You always want the hip bones wider than the shoulders and good width thurl to thurl, not pinched in the pins. Every breed develops differently, and it also depends on mineral and nutrition support, genetics, especially her dam and how she freshened, and what she is bred to.
The outer width has little relation to the inner pelvic opening too. So even super wide does can have issues if the pelvic opening isn't that wide.
I have an Alpine doe that has an 8" measurement from hip to hip (that's wide, a good average is 7") but her pelvic opening isn't that big and I have to be careful when breeding her.
On the side I have a not super impressive Boer cross doe that's as open as the Taj Mahal inside! I had to rearrange a kid during her first kidding and I think I could've gotten both arms in there and still have room for the kid