Determinants of menstrual bleeding patterns among women using natural and hormonal methods of contraception. II. The influence of individual characteristics.

Menstrual diary records were obtained from women using either a natural method of contraception, a combined or progestogen-only oral contraceptive, a vaginal ring, or a long-acting injectable (DMPA). Within each method group, multiple regression analysis was used to examine the relationships between the subjects' bleeding patterns and their age, age at menarche, ponderal index, obstetric and contraceptive history and ethnic origin. The influence of ethnic origin was described in the preceding paper. Among combined pill users, increasing age was associated with more frequent spotting episodes. In both the untreated and combined pill groups, women with a higher ponderal index had less variable bleeding-free intervals; in the vaginal ring and DMPA groups, the more obese women had shorter bleeding/spotting episodes and longer bleeding-free intervals. Among combined oral contraceptive users, the most influential variable was the time since the end of the woman's last pregnancy: subjects who had been more recently pregnant had longer, less predictable episodes and shorter intervals. Previous oral contraceptive use was associated with more predictable bleeding patterns among women currently using either type of oral pill. In the vaginal ring and DMPA groups, subjects whose last pregnancy had ended in abortion had more bleeding/spotting days and episodes than those who had had a live birth. As reported previously, bleeding patterns were more closely related to the woman's geographical region of residence than to any other factor. The associations found with other individual characteristics were often inconsistent or difficult to interpret. A number of variables which could potentially influence menstrual bleeding patterns, such as nutritional status, were not measured and therefore could not be included in the analysis. However, contraceptive method and ethnic origin may be predominant influences, overriding any other factor.