Engaged couple Mariah and Clay were diagnosed with cancer within days of each other

An engaged US couple who were diagnosed with cancer within days of each other decided to move their wedding date to so they could face treatment as husband and wife.

High school sweethearts Mariah Nelesen and Clay Slenk, from Michigan, had planned to get married in June 2022 after getting engaged in December 2020.

But their plans were thrown into turmoil after Mariah discovered she had ovarian cancer and Clay was diagnosed with leukaemia in January that year.

READ MORE: Royals unite at Commonwealth Day service, after Harry and Meghan's abrupt departure

READ MORE: Samantha was labelled 'the devil' for having a dress code at her wedding

"I got a phone call Jan 11th of this year that I had ovarian cancer," Mariah, 23, told KTLA. "That's not a call that anyone expects to receive."

Doctors found a cyst on Mariah's ovary, which turned out of be an Adult Granulosa Cell Tumour, according to the couple's GoFundMe page.

Just eight days later, Clay, 24, had bloodwork done after contracting pneumonia and was rushed to the emergency room when doctors discovered he had Acute Myeloid Leukaemia.

"If you were to ask Clay or Mariah less than six months ago what their plans were, you would hear the excitement as Mariah signed a lease to rent a place in Chicago while she planned for her wedding, finished her degree, and would be doing a paid internship in the process," the GoFundMe description reads.

READ MORE: Prince William and Kate 'excited' to be 'following in the Queen's footsteps' during Caribbean royal tour

"Clay was working daily at a job that he loved and was counting the days until he and Mariah were going to be married. They would have also shared their excitement about their new house purchase in September that they would look forward to making into their home in the months before their wedding."

After the shock double diagnosis, Mariah had surgery to remove the cancerous tumour and plans to begin chemotherapy soon.

Clay also started chemotherapy and is preparing for a stem-cell transplant to fight his "aggressive form" of leukaemia.

Because of the upcoming treatment, the couple made the decision to move their wedding date from June to April so they could be healthy on their wedding day.

READ MORE: 'We didn't know what we were in for': Sydney mum's shock after cancer diagnosis

"They determined it was best to change the wedding venue, guest list, and all other details to go forward with it as an intimate celebration due to their compromised immune systems," the message continued.

The pair have raised over $39,000 on their GoFundMe, which will go towards medical bills and lost income due to extended hospital stays.

Posting in matching shirts with the word 'FIGHTER' printed on it on Facebook, Slenk says he and his wife-to-be are preparing for a tough year — but know they will get through it.

"Mariah bought these shirts after we both were diagnosed with cancer 8 days apart," he said.

"Orange for my leukemia and teal for her ovarian cancer. This year will not be an easy year, but we are fighters."