And to add to my earlier reply, if it is Iowa law that controls the modification, the law in that state also is that inheritances may factor into a substantial change in financial condition:
Courts may “modify child, spousal, or medical support orders when there is a substantial change in circumstances.” Iowa Code § 598.21C(1) (2013). All relevant factors are considered in determining a substantial change in circumstances, including “[c]hanges in employment, earning capacity, income, or resources of a party”; a party's receipt of “an inheritance, pension, or other gift”; “[c]hanges in the residence of a party”; and “[r]emarriage of a party.” Id. § 598.21C(1)(a), (b), (f), (g); see In re Marriage of Sisson, 843 N.W.2d 866, 870 (Iowa 2014). In addition to being substantial, the changed circumstances must be material, “essentially permanent, and not within the contemplation of the court at the time of the decree.” Sisson, 843 N.W.2d at 870-71.
Marriage of Schoper, 898 N.W.2d 203 (Iowa Ct. App. 2017)(bolding added).