[Does the month of birth affect human biological development processes?]

The results of longitudinal investigations of 1,294 girls born in Görlitz in the years 1968 to 1970 included the correlation of their birth weights and menarcheal age with their months of birth. In the process we found very interesting patterns of seasonal distribution. Girls born in January had the lowest, those born in February the highest birth weight on average. Girls born in August reached their menarche at least 4 months later than those born in October. It is conceivable that the season of birth may be much more important to human development than is generally supposed.