Jenelle uploaded a selfie to Twitter on Monday night (14 April) showing herself proudly flaunting her bump in front of a bathroom mirror.
She added the caption: "29 weeks in counting #bikinishot."
After reading some of the responses to her image, she then tweeted: "Yes, I know my boob is about to fall out… It fit me when I bought it a couple of months ago. Lol. Geeze. Shoot me!"
Jenelle then tweeted a reel of different pictures, saying she'd taken loads and had tried to find one that wouldn't have people pointing out a mistake.
"Well, damn," she wrote. "I tried to pick a pic you guys wouldn't call me out for something dumb. Lmfao. Guess I #failed."
Wild child Jenelle, 21, confirmed back in February that she's pregnant with a baby boy, who has already been named Kaiser. The tot's dad is her boyfriend Nathan Griffith.
Nathan is currently serving time in jail following a DUI incident last year.
This will be Jenelle's second child. She's already mum to son Jace, although her own mother – Jace's grandmother – has full custody of him as a result of Jenelle's well-publicised wild behaviour.
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Celebrities who announced pregnancies in 2014 in pictures:
Copyright: WENN Lexie Appleby/Future Image/Bridow/Instagram