Muslims call it a marriage contract. And they are gaining popularity among American Muslims.
Americans of all faiths call similar documents prenups. And, as previously posted, they too are gaining popularity among Americans generally.
The Muslim marriage contracts in use in America today are more likely to tread into non-financial matters, the enforceability of which may remain untested in American courts – or may previously have been rejected by American courts – when outside the context of Muslim marriage contracts.
But the law may be evolving, at least in this context, according to this Lowell [MA] Sun article: Marriage contract a tool for Muslim women’s rights.
An organization of Muslim women lawyers is at work developing a model marriage contract for use among Muslim Americans.