Influence of fixed orthodontic treatment on the menstrual cycle of adult females: A prospective longitudinal study

Objective: To investigate the influence of fixed orthodontic treatment on the menstrual cycle, including menstrual cycle length (MCL) and duration of menstrual bleeding (DMB), in adult female patients. Materials and Methods: This was a prospective longitudinal study conducted in Chengdu, China. A total of 164 adult women with normal menstrual cycles were recruited in the study, with 79 patients undergoing orthodontic treatment and 85 serving as controls. Data of MCL, DMB, and accompanying symptoms were collected over six consecutive menstrual cycles in each participant. Student's t test, Chi-square test, Moses extreme reaction test, and repeated measures analysis of variance were used for statistical analysis. Results: The MCL of the first menstrual cycle (T1) was significantly elongated by 2.1 ± 0.5 days compared with baseline (P = .003, 95% CI [23.7, 20.5]). Variability of MCL of the orthodontic group at T1 was also significantly greater (range, 15-46 days) than that of the control group (range, 24-36 days) (P < .05). No significant difference in MCL was found in the subsequent five menstrual cycles (T2-T6) compared with baseline, and no significant differences in DMB or other accompanying symptoms were observed throughout the study. Conclusion: Fixed orthodontic treatment may influence the MCL of adult females in the first month after bonding, but showed no effect on DMB or subsequent MCL through the follow-ups.