Ovulation, put simply, is the release of a mature egg from one of your ovaries each menstrual cycle. Once this egg is released, it’s available to be fertilized by sperm, and conception can occur.
Contrary to popular belief however, this crucial event does NOT always occur on Day 14 of the menstrual cycle. The day of ovulation each cycle can vary from woman to woman and from cycle to cycle. In fact, in normal menstrual cycles, ovulation can occur as early as Day 8 or as late as Day 25 of the cycle.
Ironically, the day your egg is released marks the end of your fertile time, with your best chance of conception resulting from sex in the few days before ovulation. The purpose of OPK tests is to identify these fertile days preceding ovulation. OPK stands for Ovulation Predictor Kit – the little test that’s designed to help you anticipate when you’re going to ovulate and when you’re fertile.
OPK tests – how do I use them?
Urine based Ovulation Predictor Kits
Urine based OPKs come in a number of different formats – from basic paper strips through to cassettes with droppers, to a more fancy (but not necessarily any better) digital option. Regardless of the type, they are all designed to do the same thing – detect the surge in luteinizing hormone that occurs just before ovulation, as discussed above.
Depending on the type of kit that you use, you’ll need to either collect your urine in a cup, or hold a stick or test strip in your urine stream. Coloured bands (or lines) will appear on the stick or test strip to let you know whether or not the LH surge has started. Digital OPKs use easy-to-read symbols instead of coloured bands.
Saliva based Ovulation Predictor Kits
A saliva based OPK detects the increased estrogen levels that occur before you ovulate.
As your estrogen levels rise due to the developing follicle in your ovaries, so too does the salt content of your saliva. When this saliva is put on a slide to dry, the salt crystallizes to form a pattern that looks like ferns. This ‘ferning’ pattern can be observed under a microscope.
A saliva-based OPK is basically just a small, transportable microscope that typically looks like a lipstick case. Saliva is placed on the in-built slide with a clean finger or by licking the slide.
Once dry, the saliva is observed through the microscope to see if there is a ferning pattern. This is compared with examples on the manufacturer’s instructions, to determine if you’re fertile or not.