This research about fertility postponement in Portugal, between 1980 and 2006, is based in a birth order perspective. The birth order analysis reveals a larger fertility postponement in the specific birth orders than the one found in the overall mean age at childbirth. The greater expression of the fertility postponement is also confirmed by the analysis of the median age at childbirth, with more significant increases than the mean age during the same period. On the other hand, the analysis on the diversity of mother’s age reveals a two step process in thePortuguese fertility postponement: whereas during the first phase there is an increase in the ages at childbirth not associated with any tendency regarding dispersion, in a second stage the global increase in the ages at childbirth is associated with a significant trend of greater diversity in ages at childbirth.

keywords: Fertility, Fertility Postponement, Birth order.