Aims For many years, Lebanese paediatricians and gynaecologists are following American and European norms for the normal age at menarche. Up until today, there are no published studies about the age at menarche in Lebanon. In view of this, we conducted a cross-sectional study, in different regions of Lebanon, to determine the age at menarche and to find out factors affecting its onset.

Materials and methods Data was collected by self-administered questionnaires including birth date, address, gestational age, birth weight, breastfeeding, current weight and height, consanguinity, father’s profession, nationality, physical activity, diet, tobacco use, age at breast budding, age at menarche and mother’s age at menarche. Questionnaires were distributed to girls between 10 and 21 years old, in different private and official schools, chosen randomly in 5 provinces in Lebanon: Beirut, North Lebanon, Mount Lebanon, South Lebanon and Beqaa. Questions were completed by the girls and their mothers at home after informed consent.

Results More than 4247 papers were distributed and a sample of 2090 girls who have attained menarche was obtained. Results of the study were analysed using SPSS version 20.00 and showed that the mean age at menarche in Lebanon is 11.84±1.30 years whereas the mother’s mean age at menarche is 12.49±1.45 proving that the age at menarche in Lebanon has been decreasing over the last several years. In addition, significant correlations (p<0.05) of the age at menarche with the maternal age at menarche, body mass index, region, season and diet were found.

Conclusion The age at menarche in Lebanon is 11.84 years and the most important factors affecting its onset are: maternal age at menarche, body mass index, region and season. Keywords: Menarche, gestational age, body mass index, consanguinity.