snotlout being pregnant automatically grounds him + makes him prime hostage material for any hunters or other villains that make it onto dragon's edge. and they're in that whole war thing so you just know that something's gonna happen. plus like. if the baby is hiccup's. that's gonna catch viggo's interest probably. so hiccup is definitely gonna have so much to stress over!
Eh, I don't have the Dragon Riders ground themselves when they're pregnant. Hiccup is pregnant in my fic Price and he's still flying around on Toothless. In Unexpected To Say The Least, the only reason why Toothless and the other dragons tried to keep Hiccup's two feet on the ground is because that fic deals with a cryptic pregnancy, so the dragons didn't want Hiccup to get hurt and lose a baby he had no idea was even there. And in Death, Ruffnut goes along on a dangerous mission while days away from giving birth, because Hiccup was potentially in danger and she refused to stay behind.
Overall, at least when it comes to Hiccup, Ruffnut, and (especially!!!) Astrid, they wouldn't want to keep their keep feet on the ground and near their home. Hiccup would just be driven mad if he wasn't allowed to fly, Astrid refuses not to do her duties as a Dragon Rider as well and Ruffnut just simply would not want to do as she's told.
Unless she gets pampered. And I think that's where she would overlap with Snotlout.
Because, of course, the Dragon Riders would want to make sure he's safe and healthy and well-fed. Hookfang would probably fuss over him. But when it comes to grounding Snotlout, I think it'll just have to do with how much Snotlout likes to be pampered. He would insist on it and it would be a good excuse to get out of whatever chores he has to do around the Edge. (Although Hiccup would probably take him off tasks such as patrols anyways just to be safe.)
Also already did the hostage thing with Pregcup (sometimes + baby) a couple of times. So yeah, very fun whump to write about and can definitely recommend.