Iowa R. Civ. P. 1.943
A party may, without order of court, dismiss that party's own petition, counterclaim, cross-claim, cross-petition or petition of intervention, at any time up until ten days before the trial is scheduled to begin. Thereafter a party may dismiss an action or that party's claim therein only by consent of the court which may impose such terms or conditions as it deems proper; and it shall require the consent of any other party asserting a counterclaim against the movant, unless that will still remain for an independent adjudication. A dismissal under this rule shall be without prejudice, unless otherwise stated; but if made by any party who has previously dismissed an action against the same defendant, in any court of any state or of the United States, including or based on the same cause, such dismissal shall operate as an adjudication against that party on the merits, unless otherwise ordered by the court, in the interests of justice.
Iowa. R. Civ. P. 1.943