Kylie Jenner. Picture: Instagram

Kylie Jenner's plump pout could be ruined by her rumoured pregnancy, according to an expert.

The 20-year-old beauty is believed to be expecting her first child with her boyfriend Travis Scott, but Kylie - who previously admitted to getting "temporary lip fillers" during an episode of 'Keeping Up with the Kardashians' in 2015 - has been told her pregnancy might cause a change in her facial features.

READ: Kylie Jenner and Travis Scott 'figuring out' relationship

Dr Simon Ourian, a cosmetic surgeon who has previously worked with Kylie, said: "I recommend that women stop getting lip fillers as soon as they learn they are pregnant.

"No one knows the implications of lip fillers on pregnant patients since dermal fillers haven't been tested on pregnant women."

Dr Ourian explained that he would never give lip injections to a pregnant woman.

He told the New York Post newspaper's Page Six column: "I would never knowingly administer lip injections to a pregnant patient.

"In fact, it is my policy not to perform any procedures at all on pregnant women."

Despite this, the medical expert claimed Kylie's plump lips are likely to still be visible during her pregnancy.

He explained: "If a woman receives lip fillers before becoming pregnant, the results can last several months into her pregnancy, especially if she received one of the newer longer-lasting fillers.

"Additionally, many women experience naturally increased lip size during pregnancy due to increased levels of estrogen, blood flow, fluids, and swelling caused by pregnancy, regardless of whether they ever received lip fillers previously."

Meanwhile, Kylie recently revealed she had lip fillers after the first guy she kissed criticised her small pout. 

The reality star admitted she had her mouth injected to make it plumper because she felt so "insecure" about the cruel comments.

She shared: "I was 15 and I was insecure about my lips. I have really small lips. And it was like one of my first kisses and a guy was like, 'I didn't think you would be a good kisser because you have such small lips.' 

"But I took that really hard. Just when a guy you like says that, I don't know, it just really affected me. I just didn't feel desirable or pretty."