21. And Isaac entreated God concerning his wife, for she was barren, and God was entreated by him and Rebecca his wife conceived.

22. And the children moved lustily against each other with her and she said when this occurred: Why am I thus?  And she went to enquire from God. 

23. And God let her to told:  Two nations are in thy womb, and two manners of government will separate themselves from thy inwards, and one form of government will be mightier than the other, and the greater will serve the lesser.

Rav Samson Raphael Hirsch says a great deal on perek chav-gimel (23): 

Different nations need not have different forms of government.  Europe contains a number of nations but they are mostly under a form of government which basically and in principle is the same.  [Please note that this was the case during Rav Hirsch's time when practically all the countries of Europe had a form of monarchy.]  Rivka was informed that she carried two nations in her womb who would represent two different forms of social government.  The one state would build up its greatness on spirit and morals, on the humane in humans, the other would seek its greatness in cunning and strength.  Sprit and strength, morality and violence oppose each other and indeed, from birth onwards will they be in opposition to each other.  One form of government will always be more powerful than the other.  The scales will constantly sway from one to the other.  The whole of history is nothing else than a struggle as to whether spirit or sword, or as our sages put it, whether Caesarea or Jerusalem is to have the upper hand. 

The Hebrew words rav (resh-bet) never means the elder [as is commonly translated], but always: great in number and power.  In the end it will be seen that the one who had seemed to be the mightier, would had fought only for lower purposes, the material, had in reality been working for the other, had really prepared the victory for him, and will finally submit to him.  The representative of the spiritual and moral comes out of this struggle as the ultimate victor, and the representative of might and force is not destroyed, but at the end finds his own purpose served in submitting and devoting himself to the principles of the other. 

With all that said, please allow me to add a few details.  As you may recall, Esav was also known as the "red one" - Edom.  In terms of nations, Edom was the Roman Empire, and could well be the political powers in and around Italy today.  Thinking in terms of the comments by Rav Hirsch about the greater ultimately serving the lesser, we can see that although the Romans conquered Judea and carried the majority of the surviving population into captivity, they also served God in the process as the prophecies around Klal Yisrael being dispersed to the north, south, east, and west were indeed carried out by the greater - Edom.  This, of course, begs the question of whether this service has been completed.

In previous weekly commentaries, I have mentioned that I like to look for those odd little phrases that tend to stick you.  Initially, for this week, I tried to find comments for the initial words of pasuk chav-gimel which Rav Hirsch translates as "And God let her be told" while the Art Scroll Stone Edition Chumash translates this as "And God told her . . ." Unfortunately I was unable to locate any points on this but the difference is an interesting one, nevertheless.