Limit the amount of results in associated queries with Rails 3.2

I have the following query:

@books = Books.includes(:author, :pages)
              .find(:all,
                    :order => 'created_at DESC')

Let's assume my "Pages" table has fields "words, pictures". For blank pages, field "words" is NULL. There are many "Pages" records per book.

The problem with the above query, is that it retrieves ALL the pages for each book. I would like to retrieve only 1 page record for example with the condition "NOT NULL" on the "words" field. However, I don't want to exclude from the query results the Books that do not match the pages query (I have 10 books in my table and I want 10 books to be retrieved. The book.page association should be "nil" for the books where the condition does not match.)

I hope this makes sense.