When parties enter into a prenup, there is a good probability that the parties will never find out whether the contract will hold up if challenged. However, if one party feels that the original agreement was flawed, then they can file a Motion to Set Aside the prenuptial agreement once a divorce or legal separation case is filed with the Court in St. Louis County or St. Louis City. Once a Motion to challenge the prenup, then the Judge will start considering the many facets of the contract to determine if it should be enforced. Most prenups, if properly executed, will hold up in Court.