Mild breast tenderness and swelling before a period may be a normal part of a healthy menstrual cycle, according to new research from the University of British Columbia.
The one-year study followed 53 healthy women aged 20 to 41 who experienced regular menstrual cycles every 21 to 36 days. Researchers found that mild breast discomfort and slight changes in breast size typically occurred before menstruation during ovulatory cycles — when the body releases an egg.
“These symptoms are often seen as part of premenstrual syndrome (PMS), but our study shows they may actually be a normal part of the menstrual cycle,” said Dr. Azita Goshtasebi, co-author and family physician.
Lead author Dr. Mary Wood, now an internal medicine resident at UBC, said the study tracked women over an average of 13 cycles using daily symptom logs and confirmed ovulation through temperature-based analysis.
“This is the first long-term study to clearly link breast tenderness and swelling to normal ovulation,” said Dr. Jerilynn C. Prior, the study’s principal investigator. “Interestingly, women had more breast symptoms during cycles with normal ovulation compared to those with disrupted ovulation or no ovulation at all.”
Breast symptoms were recorded daily using a Menstrual Cycle Diary©. Ovulation was confirmed with the Quantitative Basal Temperature© method, which tracks subtle changes in body temperature.
Of the 694 cycles studied, 71% were classified as normally ovulatory, 26% showed short luteal phases (under 10 days), and 3% were anovulatory (no ovulation). The researchers were unable to draw conclusions about anovulatory cycles due to the small number.
The study found that the average level of breast tenderness on a 0-4 scale was 1.4. Breast swelling, measured on a 1-5 scale where 3 means no change, averaged at 4 — indicating slight but noticeable changes.
“These findings are important because they help define what a ‘normal’ menstrual experience looks like,” Dr. Wood said. “Understanding this helps identify women who may have silent ovulatory disturbances, which can lead to long-term health risks like bone loss and early heart disease.”
Dr. Sonia Shirin, a co-author and researcher at UBC’s Centre for Menstrual Cycle and Ovulation Research, added that the results were most evident when analyzing the full group of participants. When a smaller group of women with consistent ovulatory cycles was isolated, the link between symptoms and ovulation weakened, likely due to sample size.
Researchers say this work can help reshape how mild premenstrual symptoms are viewed — not necessarily as signs of a problem, but as possible indicators of healthy ovulation.
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