It's already a child, with his/her own unique DNA sequence. The only reason that abortion is legal right now is because people have dehumanized human fetuses the same way that Riddler dehumanized Jews. Murder is murder, and this is just that much worse because you are actually killing your own child, without even giving him/her a chance at life.
Having a unique DNA sequence doesn't make a mass of cells a person. In fact,
some people have two or more completely different sets of DNA. But would you consider each body part to be a separate person?
And then what about identical twins?
Also, Riddler didn't kill just Jews.