Entertainment: Teen Mom's Kailyn Lowry Shows Off Evolution of Her Baby Bump While Pregnant With Twins

Entertainment: Teen Mom's Kailyn Lowry Shows Off Evolution of Her Baby Bump While Pregnant With Twins

Entertainment: Teen Mom's Kailyn Lowry Shows Off Evolution of Her Baby Bump While Pregnant With Twins

Kailyn Lowry is bumpin' along in her pregnancy with twins.

In fact, the Teen Mom 2 star who is expecting a boy and a girl with partner Elijah Scott shared a closer look at her growing belly on Instagram Dec. 5.

One photo showed Kailyn baring her stomach in a beige crop top and matching underwear, while she was pictured with a noticeably bigger bump in second mirror selfie. Ultrasound images of her unborn twins were included in her post, as was a sonogram video that transitioned between the two babies in her belly.

The 31-year-old wrote in the caption, "evolution of the twin bump."

The siblings will join Kailyn's son Isaac, 13, with Jo Rivera; Lincoln, 9, with Javi Marroquin and Lux, 6, and Creed, 3, with Chris Lopez. She and Elijah are also parents to baby boy Rio, whose birth was announced in July. 

Babies No. 6 and No. 7 are a happy surprise for Kailyn, who previously said she had "no idea" that she would conceive so quickly after welcoming Rio.

"I mean, this is my sixth pregnancy, six and seven for me," she said on the Oct. 27 episode of her Barely Famous podcast. "And I've gotten pregnant when I'm not actually like, I've tracked my ovulation and I've gotten pregnant on days that were not my ovulation window."

Looking back at her calendar, Kailyn said she "must have got pregnant right before" leaving for her Thailand trip earlier this year.