I am not a lawyer so I cannot really give a legal advice. You may want to consult a union rep, if you have one. But from the common sense point, it does look like it might be illegal, or, at least, unethical to "force" you practice with limited training given. Also, the simple math is in play here. Some odd number of peds nurses left, so now, and OB nurse with your own responsibilities, are forced to do YOUR direct job, as well as the peds job when necessary. Will that JOB be on top of what you already have to do, thus, overtime, and, therefore, paid for it? I hope so, if not, you definitely have to do something about it.