Catelynn Lowell will apparently reveal she's pregnant during Monday night's episode of Teen Mom OG.

In a brief promo video for the next episode of Teen Mom OG, Catelynn announces to her husband Tyler Baltierra that she's expecting another baby.

"Come show daddy your pretty shirt," Catelynn says in the video to the couple's three-year-old daughter, Novalee, pointing to her shirt that reads, "I'm going to be a big sister."

"No she's not," Tyler, 26, says in disbelief.

Catelynn, 25, then laughs in the video and reassures Tyler -- whom she wed in August 2015 -- that she is truly pregnant.

"Yes she is [going to be a big sister]," Catelynn replies with a big smile while throwing down the pregnancy test.

"Oh, my God," Tyler states, putting his head down on the table.

The preview concludes with Tyler appearing shocked and emotional as Catelynn sits on his lap and kisses his face.

Tyler has voiced multiple times throughout the Teen Mom OG season that he'd love to have a third child with his wife but wants the announcement to be a surprise, Us Weekly reported.

(Catelynn and Tyler gave their first child, Carly, up for adoption when they were teenagers and the event was documented on an episode of 16 & Pregnant).

Well, Catelynn was apparently ready to grow her family as well, because during a recent episode of the MTV reality series, she had her IUD -- an intrauterine contraceptive device -- removed without Tyler knowing so she could get pregnant again and be able to keep it a secret from him at first.

Catelynn's alleged pregnancy announcement is going to air while she's in rehab for the third time in less than two years.

Earlier this month, Catelynn disclosed to her followers on Twitter that she was going back to treatment only two weeks after leaving rehab on December 30 for suicidal thoughts.
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Catelynn said she needed to "work on my trauma and getting on different meds."

She also slammed haters on social media who criticized her need for more help, tweeting on January 18, "For all u haters -- YOU DONT KNOW EVERYTHING I'VE BEEN THROUGH."

She added, "Quit acting like you know what I should be doing or shouldn't!! I'm NOT running away from my family! Those are the people I love the most! You ppl are ignorant."

Catelynn's second stint in rehab began in November 2017, when she was having the suicidal thoughts. 

Last week, reports had also surfaced that Catelynn suffered a miscarriage before she decided to enter treatment.

"I'm taking the time I need right now to take good care of myself. On November 17th I thought of every way possible to commit suicide... from wrapping a belt around my neck to just running my car into an electric pole," she told Us at the time. 

"Thank God I have a support system and a HUSBAND and a DAUGHTER. Thank God I am self aware I'm seeking treatment and I WILL get better. Anyone feeling alone you ARE NOT ALONE! This world needs all of us! We are all here for a reason."

The Conquering Chaos author has been very open on Teen Mom OG and her social media accounts about her 2016 battle with postpartum depression and anxiety. That year, the reality TV star entered rehab for the first time following the birth of Nova.