Oh sorry, that was me!
I had the DGC staying over and never got back to posting about the 13 month pregnancy.
I can't look it up at the moment but I think that the heir to the throne, Richard, Duke of York, was away fighting a war against the French. The Duchess of York supposedly became pregnant by a French archer; that child, who became Edward 1V, was accepted and succeeded to the throne.
Had he not been accepted then George Plantagenet, Duke of Clarence, and his heirs would have succeeded to the throne.
If the child had not been accepted as a royal descendant, then the Plantagenets would have continued the succession right until today through that line to Michael Abney-Hastings and his descendants.