Girls Aloud star Kimberley Walsh said she broke down during an "overwhelming" visit to a maternity ward in Uganda for Sport Relief.
The singer, who guest-edited a special issue of Now magazine for the charity, gave a frank account of the poverty she witnessed.
The 28-year-old, who joined other celebrities to climb Mount Kilimanjaro last year, was finding out how her fundraising efforts helped stricken communities in Africa.
"Although it was a sad trip, it was nice to see the difference the money we raised climbing Kilimanjaro last year has made," Walsh said in Now.
"Visiting a maternity ward in Hoima Hospital, Hoima, was one of the most difficult experiences.
"I was told the story of a woman called Jacqueline who was pregnant and had contracted malaria. She arrived there two days before we did, but her husband didn't get her to hospital in time. Both Jacqueline and her unborn baby died from what is actually a preventable disease.
"I think even though I had been on a trip like that before, and you see things in the press and on TV, none of that prepares you for the shocking reality."
Walsh said she thought she would be OK - but felt "overwhelmed" and ended up rushing outside to compose herself.
She said: "I was shocked at how much it got to me. I was overwhelmed the minute I walked in.
"In this hospital there were 20 women in a tiny room and they had all literally just given birth and had their babies lying on them and just that alone was so shocking.
"I ended up rushing outside to pull myself together. What you can't get from TV is the rawness - the feeling and the smells.
"The whole thing takes over. My cousin had a baby only three days before, but in a completely different world, so to see how people have to deal with that experience in those circumstances was really shocking.
"I did break down, but I thought I have no right to because these people are dealing with it everyday."
The full interview is in the special Sport Relief issue of Now magazine, which sees 5p from every £1.40 copy sold on UK news stands go directly to the charity.
The BBC will screen a film of Walsh's journey as part of Sport Relief on the weekend of March 19-21.
© Press Association