Mentions of a writer's pregnancies remind me of Nicholas 1st who, says Nabokov, wanted to be, to Russian writers, "a father, a godfather, a nurse, a wetnurse, a prison warden and a literary critic" (Lectures on Russian Literature, 3) or, for that matter, of the American publisher "who dreams of becoming a male nurse to his author" (Foreword to The Defence).
This being said, a writer pregnant with a composition is fairly common imagery though some authors do renew it. Poets use it (I think of Mallarmé: "Je t'apporte l'enfant d'une nuit d'Idumée" ["I bring you the child of a night of Idumea"]). A novelist pregnant with a plot or character is even more frequent. Nabokov quite often sees himself in the part, especially with eponymous heroes or heroins (Lolita/ Lolita was: "A painful birth. A difficult baby."). But other novelists do or did. I remember French novelist François Mauriac saying: "Quand j'étais gros de Thérèse" [When I was pregnant (big) with Thérèse (Thérèse Desqueyroux)"].
Didier Machu