Secondary amenorrhoea: prevalence and medical contact--a cross-sectional study from a Danish county.

OBJECTIVE: To examine the prevalence of secondary amenorrhoea and the patterns of seeking medical advice for secondary amenorrhoea in an unselected population.
DESIGN: Cross-sectional postal questionnaire study.
SETTING: County of Copenhagen, Denmark.
SUBJECTS: 3743 women, aged 15-44, selected at random from a Danish county who were asked to provide information on menstrual patterns for the preceding year, 1988. The response rate was 78%. Information from non-responders was obtained via telephone interviews.
RESULTS: One-year period prevalence of secondary amenorrhoea of more than 3 months duration was 4.6% and was 7.6%, 3.0%, and 3.7% in women aged 15-24, 25-34, and 35-44 respectively. The duration of secondary amenorrhoea was 6 months or less in 75% aged 15-34 years, but longer than 6 months in 55% of those aged 35-44 years. A social gradient was found of the prevalence of secondary amenorrhoea (odds ratio 3.3, 95% CI 1.5-8.3) in the lowest social group compared with the highest social group; controlled by age. Only 39% of women with secondary amenorrhoea had contacted a doctor. Educational level or social status did not seem to influence the frequency of medical contact in women with amenorrhoea.
CONCLUSION: Spontaneous return of the menstrual cycle occurs within 6 months in many amenorrheic women below the age of 35. The detailed investigation of secondary amenorrhoea in this age group can be postponed until it is of 6 months duration, unless there is clinical suspicion of disease. The relative infrequency with which women with secondary amenorrhoea seek medical advice constitutes an important source of selection bias in hospital-based clinical research on this topic.