Back in 2009, when Catelynn Lowell and Tyler Baltierra were expectant teenage parents, they made the difficult decision to put their child up for adoption.

Arrangements were made for daughter Carly to be taken in by a loving couple, and Catelynn and Tyler would remain involved in the girl's life via an open adoption.

But the adoptive parents obviously didn't anticipate that the Baltierras would become famous and remain reality TV stars for the next decade.

And so, what started as a civil arrangement between two sets of loving parents quickly devolved into a tense stand-off, as the couple raising Carly sought to maintain privacy while continuing to permit the girl's biological parents to remain in her life.

Over the years, Tyler and Catelynn often went long stretches of time without seeing Carly.

Longtime Teen Mom OG viewers know that the Baltierras often blamed Brandon and Teresa Davis for this fact, but Carly's adoptive parents were placed in a very difficult position, and they did what they felt they needed to do in order to ensure their daughter's privacy.

On Tuesday's episode of TMOG -- which aired on World Adoption Day -- Tyler and Catelynn were reunited with Carly, now 12.

Needless to say, the episode was one of the most emotionally-charged installments we've seen in several seasons.

"When Ty and I chose a semi open adoption at 16, I never realized how joyful and painful it would be," Catelynn explained in a voice-over.

"After Carly turned 4, the cameras weren't allowed at our visits out of respect to her adoptive parents, but now I focus on the girls having a relationship as sisters."

The visit was arranged by the Baltierras adoption counselor Dawn who helped Catelynn and Tyler cope with the wide range of conflicting emotions they experienced.

"She adores you guys so much," Dawn explained.

"You're going to be the only thing she thinks about and talks about for the next weeks. She's just going to be thinking about all these special times together. It's so meaningful."

"It doesn't get easier," a tearful Tyler observed after the visit.

"You wouldn't be human if it did," Dawn replied.

Clearly, the Baltierras' adoption arrangement has taken a considerable emotional toll over the years.

Perhaps there were even times when they wondered if it was all worth it, if they couldn't make everyone's lives easier by simply parting ways with Carly.

But according to Catelynn, she and Tyler wouldn't change a thing, especially since they've been able to share their story with so many other parents.

"I really do think that it opened the eyes for lots of people to really see how real adoption works and the struggles that birth parents go through and adoptive parents go through," Catelynn explained.

"It's not a Lifetime movie. It's authentic."

These days, it seems that the Baltierras are doing better than ever.

After years of turmoil it seems that Tyler and Catelynn's marriage is on a firm footing, and their love for one another has only been strengthened by all the tests its endured.

Still, episodes like the one we saw this week remind us that the lingering pain from their first major decision will always be with them.

Over the years, the Baltierras have fought to bury that pain, but as Catelynn's grandmother pointed out, that might not be necessary.

"You say you want to be honest with your kids. You got to be honest with her too," Deb suggested when Tyler spoke of the importance of not crying in front of Carly.

"We're always so excited to see you, but this is the sad part. It's hard to say goodbye."

Tyler and Catelynn's emotional honesty has been a gift for Teen Mom OG fans.

Perhaps it would be for Carly as well.