The MTV reality star and her husband announced the birth of their daughter on social media with a photo of the infant, named Layne.
"Happy birthday to YOU, sweet baby Layne," she captioned the photo.
DeBoer shared the same photo on his account, writing, "Happy birthday to my sweet perfect wife Chelsea DeBoer who just gave our family this beautiful blessing! Sharing the same amazing day I am so in love with our family! Our newest edition Baby Layne!!"
Houska and DeBoer welcomed their son Watson in January 2017, and Houska also has an 8-year-old daughter, Aubree Lind DeBoer, from a former relationship with ex Adam Lind.
The happy couple announced they were adding a third child to their family in March, sharing a framed ultrasound on Instagram with the words "It's a girl" above.
"....GUESS WHAT! A sweet baby girl will be joining the DeBoer clan in a few short months! We could not be more excited!" Houska captioned the photo at the time.
Since then, the 27-year-old has been sharing periodic pregnancy updates with fans, many of which have been humorous observations of her "pregnancy brain."
"The other day I drove off with my phone on the hood of my car.....two days later, I threw it away in a garbage bag and then into a dumpster," she wrote on Twitter in July. "Aubree says it's gonna end up in the toilet next #pregnancybrain #losingmymind."
Friend and co-star Kailyn Lowry quickly offered her congratulations to the new family of five, writing on Twitter, "Happy birthday to [Chelsea Houska] [heart emoji] and to sweet baby Layne. Congrats"
Fans of Teen Mom 2 were quick to offer their congratulations to the happy mother and father:
Congratulations! She looks so much like Watson! 😍😍😍— The Real Dori 🇮🇪💚🇮🇹 (@PhillyEaglesGrl) August 29, 2018
Congratulations she is gorgeous & what a really nice & different name. Hope all is well xxx xxx xx— Helen Lally (@LallyHelen) August 29, 2018
CONGRATULATIONS! SHE'S BEAUTIFUL!— WaWa Wade (@wawade520) August 29, 2018
She beautiful 😍😍😍congratulations you guys I been waiting 😍she beautiful just like aubree she got two wonderful big siblings to watch over her . One bro to kick ass if a man breaks her 💕sister to watch closely 😍 congratulations 🎉 you guys xoxo— CHELSEA (@TheTaurus87) August 29, 2018
Congratulations to the happy family!
Photo credit: Facebook/Teen Mom 2