My hormones tell me when I ovulate?!

In a perfect world, ovulation predictor kits (OPKs) would infallibly detect ovulation, and having sex while you're ovulating would inevitably lead to pregnancy. The reality is much more complicated though.

How do ovulation tests work?

OPKs can detect a surge in the production of luteinizing hormone (LH), which occurs roughly 12 - 36 hours before ovulation. By timing intercourse before and shortly after the LH surge, you can increase your odds of bringing sperm and egg together at the time when conception is most likely to occur.

But take note: OPKs do not test for ovulation. Ovulation predictor kits measure the LH surge that precedes ovulation, but can't confirm whether you have actually ovulated. Occasionally, an egg fails to emerge from its follicle after the LH surge has occurred, a condition known as LUFS (luteinized unruptured follicle syndrome).

OPKs also don't indicate whether cervical mucus is conducive to fertilisation. The mucus produced by the cervix in mid-cycle, which you experience as vaginal discharge, must have a certain consistency (clear and elastic, like egg whites) in order to provide a fertile environment for sperm to swim through. OPKs do not monitor cervical mucus.

How accurate are ovulation tests?

OPKs are more precise than other methods of monitoring ovulation. Used correctly, the major-brand OPKs are more than 97% effective in detecting an LH surge, which is used as a marker for ovulation.

Although in most cases, OPKs provide an accurate forecast of your LH surge and subsequent ovulation, they are most effective when used together with other monitoring methods. If you want to get really serious about tracking, along with an OPK, try examining your cervical mucus and charting your basal body temperature – the term refers to your lowest, or baseline, temperature, and is usually taken first thing in the morning. These methods combined can greatly increase your chances of becoming pregnant or avoiding it, but can also be quite stressful.

When should you take an ovulation test?

OPKs should be used in the middle of your cycle, during the time when you would be most likely to ovulate. How do you work that out? See below…

First to work out your cycle length, jot down the day of full flo (period not spotting). This is cycle day (CD) 1. The last day of your cycle is the day before your next full flo. You should have a cycle length of anywhere between 21-35 days. This is what is considered “normal”. If your cycle is consistently outside of this range, please speak to your health practitioner.

Now you have your cycle length.

There are 2 types of OPKs on the market

1. Dual hormone testing like the Clearblue digital “4 or more days”. It's the only ovulation test to accurately track not only luteinising hormone but also estrogen to identify your wider fertility window. By identifying more fertile days before ovulation than any with other ovulation tests, you have more opportunities to prepare to get pregnant and can plan ahead to spend quality time with your partner.

2. LH only test stips give you a narrower window but are more cost-effective. They only detect the LH surge which is 12 - 36 hours before ovulation. Sometimes this is not enough time.

Depending on your cycle length you begin testing around 5 days before you would assume ovulation. This might take a few goes, as you might be mistaken about when you ovulate. For example, my cycle is anywhere from 22 - 26 days, because I have a shorter cycle, I would begin using OPKs from CD 6, right after my flo had finished. I discovered I ovulate anywhere from CD 7 - 12.

The Pros of OPKs:

1. OPKs are convenient. Since you only need to use OPKs in the middle of your cycle, it's a little less work than other methods of tracking ovulation, such as charting your basal body temperature (BBT), which requires a daily commitment.

2. OPKs are widely available. You can get them over the counter at pharmacies, and most major supermarkets and convenience stores, without a prescription.

3. OPKs are easy to use. Ovulation kits are similar to home pregnancy tests — you simply urinate on the test stick, activating a chemical that can detect your LH surge. Most OPKs contain between five and nine test sticks.

The Cons of OPKs:

1. OPKs don't work when certain fertility drugs are present in the system. OPKs do not function reliably when injectable fertility drugs such as Pergonal or the hormone hCG (e.g., Profasi) are present in the system.

2. OPKs do not work consistently on women over 40 or if you have PCOS. Some women in their 40s, especially those approaching menopause, have increased levels of LH in their systems at all times, rendering the tests invalid.

3. OPKs don't come cheap. These kits cost between $15 and $50 depending on the brand and the number of tests included. Each is good for a single cycle.

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