Age, seasons and influence of body mass index on menarche among secondary school girls in Port Harcourt, Nigeria

Menarche is a significant marker of maturity and puberty in girls, and it is a transition influenced by different biophysical factors. This study was carried out to determine the age, seasons and the influence of body mass index (BMI) on menarche. A total of 450 girls’ between the ages of 10 and 19 years participated in the study. Age at menarche was obtained via the recall quo cross sectional method. Parameters measured were; standing height (SH), weight (Wt) and BMI. A total of 373 (82.9%) girls had their menarche in their early adolescence while 77 girls (17.1%) had their menarche in mid adolescence. Mean age at menarche was 13.17± 1.48 years. The average value for BMI was 20.35 ± 3.77 kg/m2, SH was 161.09 ± 6.16 cm, Wt was 52.53 ± 9.21kg. Overweight girls were observed to attain menarche earlier, followed by those whose mean weight was in the normal range .Subjects in the underweight category had higher age at menarche. Menarche was high in the months of August, July and January. Menarche occurs early among secondary school girls in Port Harcourt and among other factors, those associated with BMI and stress are important in the onset of the biological event.