Here's another thought (probably prompted by
mormegil's
thread and my own three children:
As stated previously, know nothing about elvish contraception, gestation, anatomy, etc, but what if Arwen and Aragorn conceived before they are married in Gondor?
Would this be a problem for the new King? Did Tolkien give examples of children born thus, and if so, are these (for lack of a better word) out-of-wedlock children shown in a better or lesser light?
Did not PJ use the fact that Arwen and Aragorn have a son later to show why Arwen decided to hang around ME a bit longer? If there was more than kissing in Rivendell, then how would they know that they, well, weren't? Would Arwen have been permitted to take the boat to Valinor if she were pregnant? Would either want to take the chance?