The response is monitored by ultrasound scans and blood tests. This causes ovulation to happen. Anxieties associated with this treatment are overstimulation of the ovaries which occurs in about 0.5 per cent of cycles. Also the rate of multiple pregnancy is increased compared to spontaneous conception. The chance of twins is approximately 20-25 per cent.
Fertilization takes place outside the woman's body.
Monitoring is again by ultrasound and blood tests . Once there are sufficient follicles of the correct size an injection of hCG is given. The eggs are removed from the ovary 36 to 40 hours later. This is done using a fine needle placed into the vagina and is performed under sedation. The eggs are fertilized with sperm in a laboratory.