What can cause cramping/sharp pains after IUI?

This depends on the mode of stimulation you had. For example, if there were several follicles present, not all of them mature necessarily because say you were stimulated with gonadotropins, then your ovary may be a little "tender" from the stimulation process, especially if your right ovary was more responsive than your left. You have to keep in mind that you have corpus luteal cyst(s) that were created when follicles created the eggs, and if so, these can also slightly "torse" especially after strenuous activity. In this scenario, if your pain gets worse and doesn't alleviate, you should go to the nearest emergency room for an evaluation....but this type of pain is usually not shap in nature. This would be of much greater concern if you were further along, as we would begin to suspect an ectopic pregnancy. For this reason, would recommend that you are followed with an hCG level as soon as you miss your period and/or suspect you're pregnant.