Shay joked in the caption: "Does this mean I’m allowed to drive in the car pool lane at all times now?"
This marks the second pregnancy for the YOU star as she sadly had a miscarriage last year.
The 32-year-old actress shared "There is something in the oven and it's not my pizza!!! WOW... It's kind of surreal processing the fact that another human is growing inside of you. It's exciting, nerve-racking, difficult and emotional all at the same time."
"Everyone waits for the right time to make the announcement and for me it wasn't until I couldn't hide it anymore and was tired of wearing over sized sweatshirts. We're beyond excited and looking forward to starting a family" added the Hollywood star.
"I've learned so much about myself and parenthood over the past 6 months, and feel like I haven't even scratched the surface! It's going to be a wild ride!!" concluded the mum-to-be.
Her former Pretty Little Liars co-stars Lucy Hale, Troian Bellisario, Ashley Benson and Janel Parrish wished the star their warm congrats.
“YAS queen 😍😍😍 I am so excited to be a mama with you and welcome this beautiful babe to the world!” Troian commented.
See the rest of her co-star's well wishes below.
See the full pregnancy announcement video here.
Congratulations to the happy couple!