Episode one: the new girl MC introduces herself to the rest of the class, going through the usual motions of a first day at school like any anime.
No obviously pregnant students appear this episode (except maybe the homeroom teacher), but they give a couple hints: The genki new best friend character talking about how they should be friends because they're all 'nakama' now, the lunch scene where said friend and other characters eat so much it surprises the MC, but then she thinks "yeah, I need to eat like that, too.", and other subvert nods to their condition.
School over, the MC goes home to parents that are very obviously worried about how everything went, more than they should be for a usual first-day-at-a-new-school anime scenario. She waves off their concerns saying that it was good and fine, and she wants to take a bath and rest a bit after school. They show the usual body-obscured shower scenes, and then skip to a close up of her lying on her bed and looking at her phone while reflecting on the days events.
She says the usual stuff about hoping everything goes well for here and wondering about the future, and that she's especially worried about the future "because..."
*camera zooms out to show her lying in her underwear face up on her bed, midsection fully exposed and showing a slight, but definitely pronounced swelling*
Roll happy theme song credits.
Episode two: now that the cat's out of the bag, they introduce the obviously pregnant cast members: the kind but responsible student council president who's six months along (who the other cast members always make fun of for always being so responsible, yet still somehow having gotten pregnant); the leader of the deliquents who's at eight months along and acts like as much of a badass now as she did before, but also shows extreme love, care, and concern for her unborn child; the 4 month along quiet girl who's shy and self concious but can't hide her growing belly any more; etc.