March 26, 2001 -- Women have often turned to the soothing warmth from a heating pad to help ease the pain of menstrual cramps. Doctors, however, say they are still trying to determine if the practice actually has some medical benefit.
"Heating pads are something that have been used and advocated in the community for years," Michael Zinger, MD, tells WebMD. "It is a home remedy that has been used for a long time, and many people believe in it, but it hasn't been sufficiently validated in an academic scientific medical setting."
Some women are said to experience pain and cramping at the beginning of their menstruation because of abnormal uterine contractions and a constriction of blood vessels in the myometrium, the smooth muscle coat of the uterus. It's possible that a heating pad could help to relax the myometrium, reducing constriction of blood vessels and improving blood flow to the uterus.
When Zinger's group tested this theory on a small group of patients, the researchers found their participants' pain often lessened over time. But they are still speculating about their results on blood flow.
"We did find a significant decrease in the amount of pain the patients had over those four hours," says Zinger, who is a clinical instructor in the department of obstetrics and gynecology at the University of Cincinnati. The percent reduction in pain compared with the start of treatment was 27% at the first hour, 43% at the second hour, and 79% at the end of the fourth hour.
The investigators measured uterine blood flow in seven patients asked to come in for a four-hour session during a painful period. Heating pads were placed on patients' lower abdomens for four hours, with a temperature maintained at about 104-107 F.
The researchers, however, did not find a change in the average blood flow. But in individual patients, those who reported the greatest reduction in pain seemed to have the most improvement in their own uterine blood flow during the testing times.
The study was presented as a scientific poster at the Society of Gynecologic Investigation annual meeting held in Toronto earlier this month.
Other physicians asked to comment on the study said they had some reservations about making conclusions from the investigation.
"This particular study is limited by a small number of patients, and it is not placebo controlled," Paula Amato, MD, tells WebMD. She is an assistant professor in the department of obstetrics and gynecology at Baylor College of Medicine in Houston.
In this study, the investigators did not compare how a heating pad could soothe menstrual pain with a placebo remedy -- or one that would not be expected to have any benefit. So there is no telling, at this point, if the patients could have experienced the relief by chance or if it was the heating pad that actually was helping.
"I have recently read an article which came to the same conclusion, that heating pads do help with primary dysmenorrhea," or menstrual pain, Amato says. In that study, however, patients didn't know whether they were getting actual treatment or placebo. Patients in that study were treated with a heating pad and the anti-inflammatory drug ibuprofen and compared with another group of patients given a heating pad and placebo.
The idea of the new study, however, is intriguing, she says, and "food for thought for future investigations."
Zinger says the study results presented at the meeting are only preliminary findings and plans are under way for a larger trial with more patients and a placebo group.