(CNN) -- Martina Navratilova was forced to abandon her charity climb of Mount Kilimanjaro in Tanzania on Thursday, after the tennis legend became unwell on day four of her first attempt to scale Africa's highest peak.
The 54-year-old hoped to finish 2010 on a high by raising more than $133,000 for the Laureus Sport for Good Foundation after a year which she has described as her "own personal 9/11."
The former women's number one was diagnosed with breast cancer in February, but has since been given the all-clear from the disease.
Navratilova began her ascent on Monday, but was forced to withdraw from the 27-strong team taking on the challenge when she felt ill 4,500 meters up Kilimanjaro.
She has been hospitalized at the Kilimanjaro Christian Medical Centre.
"I'm very sorry not to be able to complete this amazing journey," Navratilova told her official website. "I didn't make it, but I think it has been a great success as we have raised funds and awareness for the work that Laureus does."
The Czech-born player was assisted down the mountain by porters and is now being assessed in a nearby medical center.
"This is fluid in the lungs related to high altitude. It is potentially dangerous when someone is at high altitude, but once brought down, recovery is quick. Martina is doing well and will continue to do well," Dr David Silverstein said in a statement.
"There will be no effects to long-term health, and patients get back to full fitness in due course. Martina's acute condition is not reflective of her health or fitness. It occurs in some people in conditions of low oxygen."
Prior to beginning the climb Navratilova told CNN that she was "very excited" to start the challenge. She said: "I've been waiting for a year to come here."
Despite her recent health problems, altitude tests revealed that the 18-time grand slam singles champion had the lungs of a 25-year-old.
However, the Laureus team -- which includes German Paralympic cyclist Michael Teuber and British Olympic badminton medallist Gail Emms -- have had to face difficult weather of blizzards and mists over the last few days
They are continuing with the attempt and are due to reach the summit of the mountain on Saturday.
"The whole group of the climbers is very sad about Martina's situation, but at the same time we are glad to hear that she is doing fine," Teuber said.
"Now we are even more motivated and want to reach the summit also for her. I will carry the Laureus flag up to the top and stick it in the ground for her."