How ovulation tests work
Egg release from the ovaries (ovulation) is controlled by a hormone called luteinising hormone (LH). LH levels noticeably rise about 24 to 36 hours before ovulation. By using a home ovulation test to measure the LH levels in their urine, women can find out the most fertile days of their menstrual cycle, and this can help them increase their chances of getting pregnant.
Another type of home ovulation test involves testing saliva for subtle microscopic changes that occur during a woman's cycle. The test kit contains a magnifying lens that is used to examine samples of saliva, which changes appearance when the oestrogen level rises several days before ovulation.
Phases of the normal menstrual cycle
- An egg can be fertilised only for about 12 to 24 hours after ovulation. However, sperm commonly live for 3 days (and can live for up to 5 days), so a woman could conceive if intercourse took place up to 5 days before ovulation and 24 hours after.
- Most couples achieve pregnancy within the first 6 months of trying, but one in 10 couples will not conceive within a year.
- Many women incorrectly believe they are most fertile immediately after their period: instead, a woman is most fertile around ovulation, which occurs mid-cycle for the majority of women.