Prenuptial agreements have a reputation, that's for sure. One of the myths about these contracts is that they are impregnable once signed. It is as if once you signed the contract, everything is etched in stone no matter how unfair or ill-advised the contract is. But, in fact, this is just a myth. There is no truth to the idea that prenuptial agreement are immune to legal challenges.
So how, then, could a spouse challenge the validity of their prenuptial agreement? There are many circumstances that can lead to such a challenge, and the first one we'll talk about is the overall "fairness" of the contract. There has to be "conscionability" when it comes to a prenuptial agreement. The contract can't be too unbalanced and favor one spouse too much. If it does, a judge could rule that the contract is "unconscionable," meaning that part of or all of the prenup could be struck down.
There is also a time consideration before the prenup is signed. If your spouse failed to give you enough time to consider the contract before signing, or if he or she forced you or coerced you to sign the document, then it could be deemed invalid.
The contents and provisions of the document also have to be proper and compliant. If false information was provided, or if illegal provisions are included in the document, then part of or all of the prenuptial agreement could be deemed invalid.
Source: FindLaw, "Top 10 Reasons a Premarital Agreement May be Invalid," Accessed July 13, 2016