One is thae fact of her not being pregnant.
Another is the fact hidden from her.
They say truth cant be hidden forever.
Dev is postponing the disclosure of truth. Even now he wants to keep his mother in dark and is asking for Sona's cooperation. Why is he not learning lesson after watching Sona's reaction and state? Does he want his mother to undergo the same trauma?
Poor Dev has to take all this because the terrific drama that is unfolding is because of his goofiness.
I can forgive Dev for infusing such dramatic scenes at his expense.