'Teen Mom 2' season 5 trailer reveals Jenelle Evans abortion bombshell, cause of Leah Messer's daughter's disability [WATCH]

Another year, another season of Teen Mom 2. The second installation of the MTV series, and the most controversial, has been renewed for a fifth season. Today (Dec. 18), MTV premiered the first teaser trailer for the documentary, and it's already looking high on drama.

Teen Mom 2 follows the lives of Jenelle Evans, Leah Messer, Kailyn Lowry and Chelsea Houska from the second season of 16 & Pregnant as they raise their children, fall in (and out of) love and maneuver being young adult women and mothers to toddlers. It's not an easy life, as shown by MTV.

In this season's trailer, viewers finally learn that Leah's daughter Aliannah has a rare form of muscular dystrophy, and it seems like her storyline will largely focus on that and how she and her family deal with Aliannah's disability and try to give her a normal life.

Chelsea continues the baby daddy drama, as her ex-boyfriend and father of daughter Aubree is getting ready to have another child with a new woman.

Kailyn is busy being a working adult, military fiancée, pregnant and house hunting, as she tries to cram in years of life goals into one small time period. As she plans her wedding to Javi Marroquin, she struggles with family issues and finding out who is truly there for her.

And, then, there's Jenelle Evans. The troubled starlet who has been in and out of rehab and prison for a variety of offenses is back on the show. After ending season 4 by nodding off on heroin with her ex-boyfriend Kieffer Delp, it seems like life has not leveled out for her just yet. Jenelle gets married, gets pregnant and reveals one shocking thing previously unknown to viewers: she got an abortion.

Yes, the bombshell sees to have come from June 2013, when Evans got pregnant with her husband Courtland Rogers. However, the two had a rocky relationship, and Courtland got sent to prison. Soon, Jenelle started dating Nathan Griffith and decided to abort Courtland's child.

(Now, of course, Jenelle is pregnant for a fourth time with Nathan's baby, which she just announced earlier this week...)

Scandalous.

Watch the trailer for Teen Mom 2 below.

The fifth season will premiere on Jan. 21, 2014.