This is a real slavery fantasy - the slave bears the child for the owner's use (in this case to raise as her own; yes I know that you've added the twist that it would be your biological child) and remains as a slave in the household to provide menial services, such as babysitting and nursing. I suppose I could barely imagine someone actually getting into that, as a Dom/me or a sub.

In reality? Can you imagine how totally twisted that child would be? I'm glad that there are probably too many real-world impediments to trying to realize this one.