Age at menarche in Thai girls.

Age at menarche and menstrual symptoms were recorded in a sample of Thai schoolgirls in Bangkok. Using a random sampling proportional to size from this target population, structured questionnaires were offered to a sample of 15998 girls of grades 4-12. Fifty-six per cent of the study population was menarcheal during the time of study. Average mean ages by recalling age at menarche and by probit analysis were 12.51 +/- 1.17 and 12.35 +/- 1.41 years, respectively. The onset of menstruation occurred most frequently in April and October. Abdominal pain was the most common symptom during the menstrual period. Acne, malaise and back pain were other common complaints.