a bun in the oven
when someone is pregnant, especially with multiple babies, like a whole batch of meatballs in a hot oven
My aunt is a bun in the oven. She’s been eating tacos like it’s her last meal.
She texted me, 'I’m a bun in the oven, and I’m not going to let you forget it.'
That lady is a bun in the oven. She’s got a whole batch of babies in there.