Olivia Tullo was 28 when she and her husband decided to start a family. They’d bought a house; they had a puppy. They were ready.

“We started trying, and several months went by. I just had a feeling,” Tullo said. “I just knew something wasn’t right.”

Her OB-GYN recommended a fertility specialist, who eventually recommended surgery for what was determined to be endometriosis. After that, there was more trying, more tests and the discovery that she had premature ovarian failure.

"My ovaries were shutting down,” Tullo said. “And I was only 29."

Age is one of the main factors that can drive up a woman's risk of infertility, which affects approximately 10 percent of women between the ages of 15 to 44. By 40, a woman's chances of becoming pregnant drop from 90 to 67 percent; at 45, a woman has just a 15 percent shot.

But the Centers for Disease Control and Prevention estimates that in 2002, the most recent year for which data is available, 11 percent of married women under 29 also experienced infertility. In that age group, infertility is defined as one year of trying and failing to conceive.

“You are really still in your fertility peak until 31 or 32," said Dr. Pasquale Patrizio, director of the Yale Fertility Center. Most healthy young women in their 20s can rightly expect that they will be able to conceive, he said. Which can make it all the more shocking for women who cannot.

“I never thought our 20s would be so consumed and obsessed with dealing with these treatments," said Mary Roberts, now 27, who has been trying to have a baby for almost four years. "No one says their vows -- ‘through sickness and health’ -- and thinks that right after you say them you’ll test that."

Roberts is now in the very early stages of her second round of in vitro fertilization. Her first round was successful, but she miscarried at four weeks. She has been told that an autoimmune disorder is at the root of her infertility.

“It drives me insane," Roberts said. "When did it happen? How did it happen? I don’t have answers. I just know that infertility is a symptom."

There are many diagnoses offered to women like Roberts to explain their infertility: diminished ovarian reserve; ovulatory dysfunction; pelvic inflammatory disease; endometriosis (when the tissue that normally lines the inside of a woman's uterus grows outside of it and can prevent an egg and sperm from uniting). Polycystic ovarian syndrome is the most common cause of female infertility, resulting from a hormone imbalance that can disrupt normal ovulation.

"Usually in that young age group, a common factor is a tubal disease, like the fallopian tubes are blocked," said Dr. George Attia, director of the Reproductive and Fertility Center at The University of Miami Miller School of Medicine. "The other cause is the partner may have a low sperm count, or poor sperm motility.” (According to Resolve: The National Infertility Association, one third of infertility is a result of male factors.)

Some studies have focused on the role that environmental exposures, like pesticides and heavy metals, as well as behaviors such as drinking and smoking, can play in declining sperm counts, largely because those effects are easier to see and track in men.

Although many women may be labeled infertile without a clear reason behind it, one bright spot for women experiencing infertility in their 20s is that they may be more likely to get an answer to that wrenching question: “Why?”

“With younger patients, there's usually a cause rather than 'unexplained fertility,'" said Dr. James Grifo, director of the New York University Fertility Center.

But their treatment options are largely the same as those available to women who are no longer in their 20s.

Women are often prescribed drugs to promote ovulation, or they try artificial insemination or IVF. Artificial insemination is significantly cheaper (at an average of $865, according to Resolve) than the $8,000-plus per cycle paid by women doing IVF. Yet some young women do take the more expensive option.

According to the Society For Assisted Reproductive Technology, women under 35 underwent nearly 40,000 cycles of IVF using fresh embryos from non-donors in 2010, up slightly from years past.

Several fertility experts said they had never heard of a young woman being turned away from IVF or denied coverage because of their age, as is reportedly the case with a 24-year-old woman in the U.K. who says she was denied coverage for it until she turns 30. But they do say they are likely to be more conservative with younger patients.

"We might be less aggressive," Dr. Attia said. That could include taking time to work on weight loss if they think obesity is hampering ovulation, he said, or spreading each treatment out a little longer.

Occasionally, however, a woman’s young age can work against her.

"The very first doctor we saw said 'come back in a year,' and he excused us out of his office without doing one single test,'" Roberts said. At that point she and her husband had already been trying for at least that long.

"I had a lot of people say, 'Well you're lucky, because you're so young,'" said Katie Schaber, 27, who started trying when she was 23. "It upset me because in the end, it didn't work. I was young and it still didn't happen."

After four artificial inseminations and continued cysts and other health issues, she and her husband stopped pursuing treatment and put themselves on adoption lists. Schaber blogs about her experience and says the Internet can be a key resource for women seeking comfort and understanding at a time when so many of their friends are settling down and having babies.

Isolation was a real problem for Tullo, who said she lost touch with many of her friends who just couldn't connect to her experience. She and her husband have a two-month-old daughter through adoption. They stopped pursuing fertility treatments after she miscarried with identical twins last fall.

Tullo said she would like to see more frank, honest information out there for young women to help them make informed family planning decisions. But you can't force it, she said. Women have to wait until they are ready.

After all, even the best laid plans can go awry.

"Infertility at any age is difficult, but I do hold a special weakness in my heart for people in their 20s," Tullo said. "That's true infertility, when your body fails you at an age when you should be able to get pregnant."