Once they confirm that Roy is pregnant, they wait a little longer to announce the news to their families, so they try to remain discreet.
Or rather, they try, if it weren't for Jason starting to experience pregnancy symptoms. He knew of cases where people experience their partners' pregnancy symptoms. He's nauseous, has back pain, gets tired more easily, and is being much more emotionally explosive. The Batfam is worried (and paranoid) because all the tests they've done on Jason have come back negative and he refuses to talk about what's wrong with him... So far, the strongest theories are that it's some new undetectable drug or a magical phenomenon.
On the other hand, Roy can cope with pregnancy symptoms more calmly because he already knows what they are like. While Arrowfam is suspicious, it wasn't because of his symptoms, his radiant hair, or his more playful attitude... It was because Roy didn't order fish fingers (or any other type of fish dish) at the restaurant.