Maybe because just about everyone I know has fertility problems and people of that world are obsessed with finding an heir AND the previous Mrs. Bates never got preggers (as far as we know, and for all we know, she baked it in a pie and served it to our Mr. Bates), I thought it was some awkward reference to the issue of children and why for them, it might be tricky, he being a felon and murderer, her being at least high counts of obstruction of justice/police investigation and at worse, accessory to manslaughter. Wow. It just occurred to me how perfect these two are for each other if only they could really tell each other anything. They are the Bonnie and Clyde of Downtown Abbey. Thomas' head would explode.