I don't think it's about adoption, because she mentions "the shape of your back when you turned it on me, one last time", which can't be about a newborn baby. I do agree the "if I can't keep it, at least let me call it by name" line evokes a mother giving up her child, though. But actually it's meant to be about love. She's acknowledging the love she feels, even though she knows it can't last.
I don't think it's about adoption, because she mentions "the shape of your back when you turned it on me, one last time", which can't be about a newborn baby. I do agree the "if I can't keep it, at least let me call it by name" line evokes a mother giving up her child, though. But actually it's meant to be about love. She's acknowledging the love she feels, even though she knows it can't last.