A woman misdiagnosed as first overweight and then pregnant has had a 26-kilogram ovarian cyst removed from her body.

Key points: Ms Favell thought she was overweight until she was blacking out and struggling to breathe

Ms Favell thought she was overweight until she was blacking out and struggling to breathe Doctors diagnosed her as overweight and then pregnant

Doctors diagnosed her as overweight and then pregnant Ms Favell said removing the cyst left her "half the woman" she was

Keeley Favell, 28, from Swansea in Wales, said she began gaining weight in 2014, and after a couple of years looked nine months pregnant.

"I've always been chunky, but over the course of a couple of years, I gradually got this tummy," she told the BBC.

"It crept up so slowly that I didn't know anything was wrong — I just thought I was putting on timber.

"I've been with my partner Jamie Gibbins for 10 years and we did wonder a few times if I was pregnant — but we did home tests and they always ruled it out."

She said people often asked her when her baby was due, and to spare them embarrassment she lied rather than tell them she was overweight, as she believed.

But, Ms Favell wrote in a blog on Emergency Departments are for Emergencies Only, that after "numerous black outs, struggles to breathe, and drastic weight gain", family and workmates urged her to see her GP.

The doctor also initially thought she was overweight, Ms Favell said.

"Eventually, after having had numerous blood tests all of which came back inconclusive, my GP decided I must be pregnant, despite never examining me and the pregnancy blood test coming back negative," she wrote.

"Looking at me, anyone would have assumed I was 9 months pregnant, so naturally they referred me to my local hospital for a pregnancy ultrasound.

"Boy did this open a can of worms! The ultrasound led to an emergency CT scan which showed I had a large ovarian mass.

"This led to me being referred to a high risk obstetrics consultant who told me that surgery was a must, and I would be cut open from my chest bone all the way down to my pelvic bone; pretty much like an old fashioned C-Section."

On March 9 last year Ms Favell went under the knife, with what was expected to be a standard procedure taking less than 90 minutes turning into a five-hour operation as doctors removed what turned out to be a 26-kilogram benign cyst, which she described as a "medical alien".

Ms Favell said her family was stunned to see her changed appearance after the procedure.

"The shock on my family's faces said it all; I was literally half the woman I was going down," she wrote.

She told the BBC the cyst, which she called Mr Whippy, had left her with a large scar and stretch marks, but said she would still be able to have children.

"I lost sight of how difficult even simple things like driving a car or walking up the stairs had become," she said.

"Losing my lump gave me my life back. I can't thank my surgeon enough."