Iowa Code § 123.91: Second and subsequent conviction.

Unless otherwise provided by law, a person who has been convicted in a criminal action in any court of record of a violation of a provision of this chapter, except for a violation of section 123.46, or a provision of the laws of the United States or of any other state relating to alcoholic liquors, wine, or beer, and who is thereafter convicted of a subsequent criminal offense against any provision of this chapter is guilty of the following offenses:

1. For the second conviction, a serious misdemeanor.

2. For the third and each subsequent conviction, an aggravated misdemeanor.