Our results are consistent with previous studies that found an association between lower birth weight and early menarche.12,15,18,21 However, a few other studies reported associations only with having been small for gestational age16,17 or having had lower birth weight and longer birth length.19,23 A study of white and Asian girls reported that younger age at menarche was not associated with low birth weight or preterm status, although nonsignificant associations in that direction were present.25 We had a high proportion of women with missing data on gestational age and birth weight. However, after imputation of missing data, adjustment for preterm status did not affect the low birth weight association with early menarche. Associations with low birth weight may be influenced by later growth, but we had only crude data on pre-pubertal growth. In particular, one study reported that the association with birth weight varied by childhood body size.24 Three studies found that subsequent infancy or pre-pubertal growth, but not birth weight, was associated with age at menarche,11,20,22 although two of these studies noted nonsignificant associations between high birth weight and age at menarche after accounting for subsequent growth.20,22
