It's probably a likely scenario, but my gut tells me that they will hold off even if it's mostly subconsciously...I'm sure they have at least a working knowledge of when the most fertile times of her cycle would be, and now that they have firsthand knowledge of the pain which comes from the sort of loss they went through, they may just instinctively shy away from another pregnancy right away.
While I recognize that even an early miscarriage such as Lauren had can be every bit as painful under some circumstances, much of that depends on how much effort went into the conception. A first-time miscarriage after a conception within the first two or three months of marriage is totally different - even if the pregnancy was a planned and joyous thing - than a miscarriage a long period of trying, or after multiple lost pregnancies. And losing a baby at 20 months, fully-formed yet non-viable, has simply got to be rougher, no matter what, than losing a barely formed jellybean of a fetus which might still easily be overlooked as a heavy period unless one was making a habitual use of pee-sticks. Point being that as much as she might think that she and Joy suffered an equal loss, Lauren has no clue. Which is why, I think, she could move right on to another try where Joy might need more time.
As I say, it might be more subconscious than otherwise, but I just feel that Joy and Austin will be giving it a little bit more time.