IUI involves a laboratory procedure to separate fast moving sperm from more sluggish or non-moving sperm. IUI can only begin once it has been confirmed that the fallopian tubes are open and healthy. If someone using fertility drugs to stimulate ovulation vaginal ultrasound scans are used to track the development of eggs. If not using fertility drugs IUI will be performed between day 12 and day 16 of the monthly cycle. The fast-moving sperm will be inserted through the catheter.