ue, though: Almost all women experience retrograde menstruation, so according to Patzkowsky, doctors don't know why some get endo and others don't. Some researchers think an imbalance in reproductive hormones might be to blame, while others suggest that a faulty immune system—which would normally curb the growth of endometrial cells outside their normal locale—may be responsible. Risk factors for endo include long periods (more than seven days), short cycles (less than 27 days), and having a family member who has endo.
3. PAIN IS A CLASSIC SYMPTOM …
Some women with endo feel pain in the back or chest, and others experience discomfort during or after sex or have painful, heavy periods. Since the pelvic region serves as a crossroads for a variety of organ systems, discomfort when urinating or having bowel movements is common. Some endo sufferers have a concurrent—but not the same—condition called adenomyosis, in which endometrial tissues grow into the muscular wall of the uterus. Endo can also cause large painful cysts on a woman's ovaries, called endometriomas. Often called "chocolate cysts," due to their dark, chocolatey appearance, endometriomas are noncancerous, fluid-filled growths that typically form deep within the ovaries. Mysteriously, some women experience no pain at all, Patzkowsky says. One study found that nearly 90 percent of women with endo experience depression and anxiety. According to some mice studies, it's possible that endo reprograms the brain, making women more vulnerable to mental health problems—although other researchers think the depression and anxiety are more to do with the pain and fertility problems.
4. … AND SOME WOMEN CAN EVEN EXPERIENCE INFERTILITY.
As many as half of all infertile women have endo, and up to 50 percent of women with endo are infertile—but doctors aren't sure how the condition affects a woman's ability to get pregnant. Endo lesions can block or scar a woman's reproductive organs, making it harder for the egg and sperm to meet up, but it's also possible that the scarring prevents the endometrium from developing properly each month, preventing implantation. Other theories suggest that the inflammatory milieu that accompanies endo creates an unfavorable environment for pregnancy.
5. MANY WOMEN WITH ENDO GO UNDIAGNOSED.
Up to one in 10 of all pubescent girls and women worldwide have endo. In the U.S., that translates to some 6.5 million females of reproductive age. Some experts say the number is higher because many women go undiagnosed. That's because some women confuse the pain of endometriosis with normal period pain, and others just don't talk about it. On the other hand, "Not all menstrual pain is endo," Patzkowsky says.
6. THERE ARE SEVERAL WAYS TO LOOK FOR ENDO, BUT ONLY ONE WAY TO BE SURE.
The first step is usually a pelvic exam. The doctor will feel for cysts or areas of scar tissue behind a woman's uterus, in an area called the Pouch of Douglas, a common site of endometrial lesions. If the doctor suspects endo, an ultrasound or MRI will often provide more information. The only sure way to diagnose endo, however, is laparoscopy with biopsy—a minimally invasive surgical procedure that allows a doctor to view a woman's internal organs using a small camera and take tissue samples (biopsies) for testing. Laparoscopy is considered the gold standard of endo diagnosis.
Diagnosis also involves determining the stage of the disease based upon the location, size, and depth of the lesions; the presence and size of endometriomas in the ovaries; and the presence of scar tissue. Most women have mild scarring and only superficial lesions, indicating that they have minimal or mild endo. Women with endometriomas and more severe scarring have moderate or severe endometriosis.
In an odd twist, "The stages don’t necessarily correlate with the types of symptoms or degree of pain a woman experiences," Patzkowsky says. For some women, a further element of diagnosis is determining her likelihood of getting pregnant, using the Endometriosis Fertility Index [PDF], a scoring system that considers 