During the IVF cycle, the woman undergoes ovarian stimulation which is carefully monitored by ultrasound scans and blood tests. Following an injection to mature the eggs (oocytes) within each follicle, the eggs are recovered from the ovaries, usually under sedation. These eggs are cultured overnight with sperm from the patient's partner (or with donor sperm) and the resulting embryos are transferred two or three days later to the uterus. If there are minor sperm problems, a higher concentration of sperm may be used in an attempt to improve the fertilisation rate. In some cases, IVF may not be possible due to very poor quality sperm and ICSI treatment would be advised.