Is body mass index associated with irregular menstruation: a questionnaire study?

Irregular menstrual cycles including the length of cycles and menses, and heavy menstrual blood loss are linked to many gynaecological diseases. Obesity has been reported to be associated with irregular menstrual cycles. However, to date, most studies investigating this association are focused on adolescence or university students. Whether this association is also seen in adult women, especially women who had a history of birth has not been fully investigated.

Questionnaire data were collected from 1012 women aged 17 to 53 years. Data on age, weight and height, gravida, the length of menstrual cycles and menses, and the number of pads used during menses were collected. Factors associated with menstrual cycle according to BMI categories were analysed.

There were no differences in the length of menstrual cycles and menses in women of different body mass index (BMI) groups. However, there was a significant difference in menstrual blood loss in women of different BMI categories. The odds ratio of having heavy menstrual blood loss in obese women was 2.28 (95% CL: 1.244, 4.193), compared to women with normal weight, while there was no difference in the odds ratio of having heavy menstrual blood loss in overweight, compared to normal weight, women. In contrast, the odds ratio of having heavy menstrual blood loss in underweight women was 0.4034 (95% CL: 0.224, 0.725), compared to women with normal weight.

Although BMI was not correlated with the length of menstrual cycle and menses, BMI is positively associated with menstrual blood loss. Our data suggest that BMI influences menstrual blood loss in women of reproductive age and weight control is important in women's reproductive years.