Its hard to say, have they gotten larger recently? I'm no expert and I don't even know if swords have a visible gravid spot or not but my guppies spot gets almost pitch black when they are pregnant. Also I've noticed that about a week before she drops she eats like a pig! Also, my guppies "balloon up" when they are pregnant. Looks like they swallowed a sugar cube when looking at her from the front. Really boxed shape to her belly.
My mama fish always liked pooping a lot before she gave birth lol.