The first part of the menstrual cycle can vary in length before ovulation, but the second part of the cycle (called the luteal phase) is almost always 13-14 days.
Therefore, it would be important to identify the days of maximum fertility by determining the day of ovulation.
If a woman has regular monthly cycles, she is considered to be ovulatory compared to someone with irregular cycles who clearly has an ovulation disorder.
Ovulation tests function by detecting the reproductive hormone LH – or luteinizing hormone. Just before ovulation, women experience an “LH surge” – a brief, marked increase in the amount of luteinizing hormone in their systems. Ovulation test kits detect this sudden LH surge, allowing you to predict, with great accuracy, when you will ovulate.
A positive on an ovulation test indicates that a woman will most likely become fertile over the next 3 days – with peak fertility at 24 to 36 hours after the LH, or positive ovulation test.
Some fertility medications can however confound results. For example, Clomid can cause a false positive ovulation test if you begin testing too early in your cycle. Once you receive a positive result, we recommend having intercourse daily over the next 3 to 4 days.
At the start of your cycle, the body starts to make follicle-stimulating hormone (FSH). FSH facilitates the production of a follicle on the ovaries. The follicle holds the ovum, helping it grow and mature.
As the menstrual cycle progresses – and when a follicle has adequately matured – an increase of luteinizing hormone (the LH surge) causes the follicle to open and the ovum is released into the fallopian tube.
Ovulation is the moment the mature ovum is released. And this is why knowing when you ovulate allows you to know that you are fertile.