The age at menarche and several menstrual symptoms were reported by
516 Portuguese school girls who took part in a cross-sectional anthropometric study in
Coimbra, Portugal. The mean ages of menarche calculated using the recall method and
also using probit analysis were 12.53 1.27 and 12.03 1.26 years, respectively. Parents’
educational level, place of residence and size of the family did not have any significant effect
on the mean age at menarche in this sample of adolescents. The order of birth was the only
variable that indicated a significative effect: the firstborns reported a lower mean age at
menarche (12.34 years) than the later borns (12.6 years). In this sample, 47% of the girls had
a cycle length of 529 days, 23.4% had irregular cycles, 59% reported that the duration of
bleeding was 3–5 days and the majority, 49%, did not report any pain during the bleeding
days. However, 14.3% and 24.45% reported severe and medium pain. The age at menarche
has declined from 15.0 (girls born in 1880–1890) to 12.03 (girls born in 1970–1980) years in
the Portuguese population. This decrease in age, and also the lack of influence of the family
characteristics, appear as a result of the great improvements in the social and economic
living conditions that occurred in Portugal, especially after the 1970s. These improvements
are mainly related to better nutrition and better health care along with many other
environmental factors
