Pure ‘Natural’ IVF is defined as IVF using no stimulation drugs. The technique relies on a woman naturally growing an egg in the ovary with her natural menstrual cycle hormones. The only medications used are to control and time ovulation so that the egg can be harvested in theatre with the patient asleep. Once the egg is harvested then usually ICSI is undertaken to aid fertilisation, before culturing the embryo on for transfer back into the womb. The success rates of Natural IVF are low as only one egg is usually retrieved. It has proven popular for patients unable or not willing to use stimulation drugs.