China's Zheng Qinwen said severe stomach cramps ruined her hopes of completing a shock French Open win against world number one Iga Swiatek on Monday and left her "wishing I was a man".
Zheng, just 19 and playing in her first Roland Garros, took the first set off the top seed before slipping to a 6-7 (5/7), 6-0, 6-2 defeat in their last-16 tie.
The world number 74 had needed a medical timeout to strap her injured right leg early in the second set but she revealed that was the least of her concerns.
"It's just girl things," Zheng said in reference to her menstrual pain.
"The first day is always so tough and then I have to do sport and I always have so much pain in the first day.
"I couldn't go against my nature. I wish I can be a man so that I don't have to suffer from this. It's tough."
In an 82-minute opening set, Zheng saved five set points, had two of her own and then clawed her way back from 2/5 down in the tiebreak to stun the top seed.
It was the first set lost by Swiatek since April 23, when she was stretched by Liudmila Samsonova in the semi-finals in Stuttgart.
As the 2020 Roland Garros champion's streak looked in peril, Zheng required a medical timeout at 0-3 in the second set for a leg injury.
Zheng, who had defeated 2018 champion Simona Halep on her way to the fourth round, returned with her right thigh heavily strapped and quickly dropped the second set.
Swiatek carved out a double break in the decider against her tiring opponent, whose physical problems contributed to her 46 unforced errors.
"The leg made it tough," added Zheng. "But that compared to the stomach was easy. I cannot play my tennis because the stomach was too much painful.
"I really give my best on court, it's just tough."
Swiatek extended her winning streak to 32 matches to equal the third best winning streak this century set by Justine Henin 14 years ago.
"Zheng played amazing tennis," said Swiatek after reaching the quarter-finals for a third successive year.
"I was surprised with some of her shots, her top spin was amazing. Huge congrats to her. I am happy to come back after a frustrating first set when I had the lead.
"I am proud to be still in the tournament."
Swiatek will face US 11th seed Jessica Pegula for a place in the semi-finals.