Sarah Joyce was in her physical and reproductive prime, a competitive long-distance runner in her 20s, but when she tried to get pregnant, her body failed her.
At the height of her training, the petite athlete from Indianapolis ran 60 miles a week and weighed in at 85 pounds, with not an ounce of body fat.
Like other female athletes, the physical demands she placed on her body over a lifetime of sports and training for two marathons had taken its toll. By 2009, she had dropped 10 pounds off her 5-foot, 1-inch frame.
When Joyce arrived at Genesis Fertility and Reproduction in New York City, where she eventually conceived, she was diagnosed with hypothalamic amenorrhea. Her periods had stopped because her body was no longer making the estrogen to produce eggs.
As women are increasingly involved in competitive sports or rigorous recreational activities, being too fit can hurt pregnancy chances, according to fertility specialists.
Now, at 30, and with a newborn daughter, Joyce's hindsight is 20-20.
"I may have been too intense and I think if I try again to have another baby, I will change my regimen," she said.
According to Dr. David Hoffman, a IVF Florida Reproductive Associates, female athletes are more likely to have ovulation and menstruation disorders that thwart conception.
"A lot of them are runners and ballet dancers because they starve themselves, and gymnasts with no body fat -- anyone who takes anything to the extreme," he said.
Hoffman knows firsthand. He treated nine-time swimming medalist and Olympic swimmer Dara Torres when she was trying to conceive. She made a dramatic comeback at the age of 41 at the 2008 Games in Beijing.
Torres became a hero to millions of American women when she spoke out about the trouble she had conceiving her now 4-year-old daughter, Tessa Grace, the daughter she shares with Hoffman. [Hoffman did not treat Torres for her successful pregnancy.]
Just this week, " target="external">tennis player Gigi Fernandez admitted publicly that she had seven failed fertility treatments before conceiving with her partner, and doctors blamed it on her athletic career.
The winner of 17 Grand Slam doubles titles before she retired number one at the age of 33 in 1997, Fernandez was told her eggs were told old.
"It was crushing," Fernandez told the New York Times. "I felt almost like I wished I would have never played tennis.
"As an athlete, you have this attitude, 'I can do anything with my body,'" she said. "That's how you think. So your biological clock is ticking, but you're in denial."
Fernandez finally became pregnant in 2008 using donated eggs and sperm, giving birth to twins after her 45th birthday.
About 1 in 6 women or 7.3 million couples have difficulty conceiving a child, according to the " target="external">American Fertility Association (AFA).
Reproductive specialists say about 12 percent of those infertile women are athletes, and the problem is becoming more acute now that more women are testing the limits of their body -- and their biological clock.
"Most of the problems we see are low body fat or over-exercising and getting infrequent periods or they lose them altogether," said Hoffman. "In the brain, the hypothalamus just goes ice cold. It's like a stress reaction -- fight or flight."