Teen Mom OG finale preview: Catelynn goes into labor, but will Tyler get her to the hospital on time?

Babies can be demanding — even before they're out of the womb.

In this exclusive preview of Tuesday's Teen Mom OG finale (8 p.m. on MTV), Catelynn Baltierra goes into labor with her fourth child, and the baby seems to be in a real hurry to get out.

"I started having contractions, and my labor goes quick," explains Catelynn. "So my doctor wants me to go to the hospital now."

But first she and her husband Tyler need to wait until Tyler's mom, Kim, can come watch their two little girls, Nova and Vaeda, who are sound asleep. Once Kim arrives, it's 9:45 p.m., and Catelynn's contractions are coming fast.

"How far apart are they?" asks Tyler, as the two drive to the hospital. "It's like four minutes," Catelynn replies. "S---," mutters Tyler, hitting the gas. Watch the full preview below.

Catelynn and Tyler were both 17 when they had their first daughter, Carly, who they placed for adoption in 2009. The two Michigan residents married in 2015, and in February of this year they announced they were pregnant with their "last and final" child.

But will their fourth daughter be born in a minivan, or the hospital? We'll find out in Tuesday's finale.

Sign up for Entertainment Weekly's free daily newsletter to get breaking TV news, exclusive first looks, recaps, reviews, interviews with your favorite stars, and more.

Related content:

• Teen Mom OG's Catelynn Baltierra suffers miscarriage: 'I miss my baby'
• Tyler explains why he didn't write Carly a letter in Teen Mom OG sneak preview
• Amber walks off Teen Mom OG reunion, because of course she did