姉は妊娠しています。（「身重」is not wrong, but we don't usually say like that.）
There are some things that I would you like to know. 身重だ ; Sounds like kind of negative. 妊娠している ; normal おなかにあかちゃんがいる She's having a baby. ; It could be my favorite expression if my sister would have done.
There are some things that I would you like to know.
身重だ ; Sounds like kind of negative.
妊娠している ; normal
おなかにあかちゃんがいる She's having a baby. ; It could be my favorite expression if my sister would have done.