Just to clarify, as mentioned, it is permissible to remove a diseased or injured organ even if regrettably, it contains an embryonic person. This is the core of the double effect, a good act (removal of diseased organ to regain health) with a predictable or foreseeable bad end (death of the embryo). The bad end cannot be intended, it merely must be incidental, as it is in this case.
On the other hand, one cannot directly attack the embryo with chemicals, etc, if the embryo is alive. This is a bad act (murder) with a good end (health of the mother). This would be an immoral act as the primary act (murder of the embryo) is always wrong.