The star is clearly fond of her 'bun' nickname, as she announced she was expecting with this tongue-in-cheek photo last week.
"Well would you look at that. There's a bun in my oven," she wrote on Instagram. "Not quite ready to take it out just yet. Should be fully baked come Spring time."
Megan and Shaun are already parents to two-year-old River. Congratulations to the growing family!