All four of the original girls of "Teen Mom 2" are now mothers of three. Just over a year after Chelsea Houska welcomed her second child, the first for husband Cole DeBoer, the longtime reality star took to her Instagram page and announced she and DeBoer were expecting a baby girl.

“GUESS WHAT!" Houska wrote in the caption of a sonogram photo on March 15. "A sweet baby girl will be joining the DeBoer clan in a few short months! We could not be more excited!”

Chelsea Houska and Cole DeBoer tied the knot in October of 2015 and welcomed their first child, son Watson Cole DeBoer, in January of last year. After the child's birth, the couple had been seen discussing expanding their family further on "Teen Mom 2" and giving Houska's oldest daughter, eight-year-old Aubree [VIDEO], another sibling.

Chelsea Houska sparked pregnancy rumors earlier this year

Although Houska waited to confirm her baby news until last night, fans have been suspecting she may be pregnant for the past several weeks due to the frequent photos [VIDEO] she's been sharing of herself in baggy clothing. “[Chelsea] was keeping it quiet, and hadn’t told many people,” a source told Radar Online, also on March 15. “A few ['Teen Mom 2'] crew members knew, but not everyone at MTV.”

During the last season of the show, Houska spoke of her baby fever and her husband Cole DeBoer made it clear that he was on board with having another child whenever she was ready. So, as fans have now seen, Houska didn't waste any time and in "a few short months," as she explained, she will welcome a third child.

Chelsea Houska and Cole DeBoer are keeping their private life to themselves

While Houska and DeBoer are still appearing on "Teen Mom 2" in full-time roles, they have taken a much different approach to reality television than many of their co-stars and opted to keep a lot of their special moments, including their engagement and their wedding, off-camera.

Meanwhile, Kailyn Lowry, Jenelle Evans, and Leah Messer have all gotten married on the show. A number of "OG" stars, including Ryan Edwards, Maci Bookout, and Catelynn Lowell, have also tied the knot on the MTV reality series. That said, Houska does her best to keep her fans in the loop with her life at home and shares frequent family photos on Instagram.

Chelsea Houska, Cole DeBoer, and their growing family, including Aubree and Watson, are expected to return to MTV for a new season of "Teen Mom 2" in the coming months.