Pelvic pain is a symptom of endometriosis, a disorder that affects the uterus lining. About 6.3 million women in their reproductive age in the United States are affected by this, according to the Endometriosis Association, but a new study says that there could be more cases that remain unreported.

"Our study suggests that many reproductive-age women are experiencing, but not reporting some form of pelvic pain," said  Karen Schliep of the National Institute of Child Health and Development in a press release. "If they aren't doing so already, gynecologists may want to ask their patients if they're experiencing pain, as well as the type and precise location of the pain, and offer treatment as appropriate. Similarly, women should let their doctors know if they're in pain." 

In this study, researchers surveyed 473 women between the ages of 18 and 44 before they had either a surgery or an imaging procedure for pelvic-related concerns. They also asked patients about any mass or lump in the pelvic region, menstrual cycles and irregularities, and infertility or tubal sterilization. The women were also asked to locate the pain they felt in their body.

Researchers found that nearly a third of the women reported chronic and cyclic pain that appears during the peak of a menstrual cycle. At least 30 percent said that they experienced this pain for more than six months, even as some of the women had no known pelvic condition. Three percent said they had none of the 17 types of pain the researchers asked about, while 60 percent said they had six or more of these pains.

"Future research should explore causes of pelvic pain among women who seek out gynecologic care but with no apparent gynecologic pathology," the researchers outlined in their study.

"Given our and other's research showing little correlation between pelvic pain and American Society for Reproductive Medicine staging [criteria] among women with endometriosis, further development and use of a classification system that can better predict outcomes for endometriosis patients with pelvic pain for both surgical and nonsurgical treatment is needed."

The findings were published in the Journal of Human Reproduction.