wife and i are getting divorce. she got pregnant before we got married and she says the kid isnt mine, can we still do an unconstested divorce

Well, It doesn't need to be "contested," you can both agree on everything, but you will need to disestablish you paternity as well as complete the divorce, so you will need to include the child in the divorce papers. That means you will not be able to use the documents supplied by the Iowa Supreme Court for simple divorces with no children. You also need to be careful that your paternity is disestablished properly, or you could be on the hook for child support and other obligations.