How important is timing of the insemination?
The precise timing of insemination is very important.The Eggs are fertilizable for only about 12-24 hours after ovulation. Therefore, insemination must be properly timed while the eggs are still viable. IUI is done either when ovulation is imminent or just after.
There are several methods available for timing insemination in natural cycles. These include; measurements of basal body temperature (least accurate method), assessment of cervical mucus (not reliable), detection of the LH surge in the urine or blood, and ultrasound scans.
Most infertility clinics time insemination in natural cycles by ultrasound scans and detection of LH surge, as these are the most accurate methods. Insemination is usually performed at 24 and 48 hours after urine LH surge. For stimulated cycles insemination is usually performed about 36- 40 hours after hCG injection.