Hello Gaspare, I have no regulations for such far distance marriages (Ferntrauung) but I don´t think that it has been necessary that the woman did give birth to a child.
Did find https://de.wikipedia.org/wiki/Deutsches_Eherecht_im_Zweiten_Weltkrieg (unfortunately in German) and there is nothing mentioned of a child needed.
Concerning the "death marriage" it is right, there has been a change during the war, that a child from this alliance was necesary and only the child had the right to inherit not the wife.
Regards,

wotan, gd.c-b#105

"Never look for sqare eggs" as a late owner of an original FHH-dagger used to say.