Usually (at least for me) I lose what the baby weights of course then the fluid and placenta etc. Comes out to be about the same as the baby. Like with my son he was 8ib10oz and I lost 17 pounds at birth and my daughter was 7ib14oz and I lost 15 at birth.
I only gained 8-9 lbs with each of my first two and I lost 10-11 lbs at birth. The placenta is only about 2 lbs i think so you should only lose what the baby weighs plus that unless you also have alot of fluid. My mom lost 50 lbs when I was born due to having so much fluid.
I gained 23lbs with my first and lost all but 5lbs within the first 10 days postpartum. Baby was 8lb9oz. Plus placenta is about1-2lbs, amniotic fluid is about 1lb, extra blood weighs quite a bit and you can retain water (think swelling) which I can guarantee you'll sweat out in the first week.
With my first the day after I had him I had lost 30lb I don't know how or why I know I had a lot of extra fluid and he was 7#14oz so that might be it. My second and third about 15 I haven't had this one yet but I have not gained any and she is measuring 6lb I'm 34 weeks