A rare condition caused this woman's baby bump to grow 'inside'.

Yiota Kouzoukas is six months pregnant but a rare condition means her baby bump looks remarkably tiny.

After receiving some comments about her unusually small baby bump, Kouzoukas decided to address them on Instagram.

The mum-to-be explained that a “tilted” uterus has caused her baby bump to grow on the inside rather than the outside.

According to Better Health Victoria, a tilted or retroverted uterus is a condition in which the uterus is tipped backwards so that it aims towards the rectum instead of forward towards the belly.

A post shared by Yiota Kouzoukas (@yiota) on Oct 9, 2017 at 2:53am PDT

“Not that I’m upset/affected by these comments at all, but more for the reason of educating in the hope that some people are less judgemental [sic] on others and even themselves,” she wrote.

“For the first 4 months of my pregnancy, my uterus was retroverted/tilted which means that I was growing backwards into my body rather than outwards.

“Most people with this type of uterus tilt forward at around 12 weeks and continue growing outwards like you normally would. My uterus didn’t “flip forward” until well into being 4 months pregnant because of the backwards tilted position paired with decade old endometriosis scarring that I have on my uterosacral ligaments.”

Kouzoukas explained that these ligaments were acting like “anchors” keeping her uterus on the “inside” rather than the “outside”.

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Now she’s six months pregnant, Kouzoukas’ baby bump is growing forward as the scarring on her ligaments slowly breaks down.

“My torso is also short and my stomach is naturally toned which is keeping my belly super tight, so I’ve had to personally stop all ab exercises to avoid any issues with possible ab separation,” she explained.

“This is for me personally, as instructed by my doctor and is in no way a blanket rule for anyone else. I’m perfectly healthy, baby is perfectly healthy and that’s all that matters. Our bodies and bumps are all different and our shapes and sizes are all different too.”

Kouzoukas’ followers thanked her for being so open and raising awareness about this unusual condition.

“I am going through the exact same thing now! My uterus was incarcerated BC of endometriosis and tilted uterus. It was pretty painful for a few weeks. But you look great!! People need to keep their negative comments to themselves,” one person commented.

“We all grow babies differently but all with the same dreams of a happy and healthy baby,” added someone else.