After full disclosure, the second most important element to fortify your prenup is time. That is the parties must have adequate time before the wedding to understand, negotiate and consider the agreement they are signing.
If the prenup is presented the day before the wedding, after the invitations have been mailed, the wedding gown paid for, and the banquet hall rented, it could be challenged on the basis of duress. The challenger might say something like, “I didn’t understand it and I didn’t read it. I just signed it so the wedding could go on.”
The way to defend a prenup from this challenge is to start negotiating long before the wedding. Keep drafts and other documents. Place a clause in the agreement that says the parties have negotiated the terms for a long time before the wedding, each has consulted a lawyer or has had an opportunity to do so, each understands the provisions of the agreement, and neither feels any duress or pressure to sign.