top of page

Are you tuned in to your fertile signs?

The market for ovulation predictor kits is massive, with 1000's of people relying on them month in, month out, to tell them when they are most fertile. But is this the best, and most reliable way of tracking your fertile period?

How does an actual menstrual cycle work?

In order to understand how OPKs work, and how your cycle is structured, its good to go back to basics. Menstrual cycles can be of varying lengths, however they are all formed of the same structure (although if your cycles are irregular, all stages may not take place). The first half of your cycle is called the 'follicular' phase because this is when the dominant follicle is going through it's final development on your ovary.

As this follicle grows, it secretes a greater amount of oestrogen which helps to thicken the lining of the uterus. Once this level reaches a critical point, it triggers a change in the Luteinising Hormone (LH) secretion that leads to ovulation occurring. This surge in LH is what is picked up (usually) by the OPKs.

After ovulation, the 'luteal' phase begins and the now empty follicle starts to release a hormone called progesterone. This hormone should stay high until implantation occurs, or if no implantation occurs, it will start to drop and you will get your period.

The OPKs are designed to register the surge in LH, and when this occurs, ovulation will usually happen 24 - 36 hours later.


  • OPKs are not always accurate. Ovulation may have either already occurred, or may occur much later than 36 hours after the observed surge.

  • OPKs do NOT tell you that ovulation has occurred. The only way to really know this is through a progesterone test 7 days after ovulation was expected.

  • It is easy to miss the LH surge unless you are testing more than once a day.

  • You may miss some of your fertile days as they may occur before your LH surge.

SO, what can you do??

Tune into your body's signs

You can still use OPKs if you want - they are useful as a second source of information - but tuning into your body's signs that are telling you ovulation is about to, or has, occurred, has been shown to be just as reliable.

Cervical fluid

Checking your cervical fluid should not be something that you shy away from. It's an amazing tool for you to use to identify when your body is getting ready for ovulation.

As oestrogen levels rise in the first half of our cycle this leads to changes in the consistency of the cervical fluid. This happens so that, at our peak fertile time, the cervical fluid has a consistency that helps the sperm to swim up through the cervix. After ovulation, increases in progesterone make the mucus becomes thicker and sticky to prevent anything else passing through the cervix. Understanding and recognising these changes can help you to identify your fertile period.

The pattern of changes that our fluid goes through are as follows:

>Dry / sticky


>Wet / watery

>Raw ‘egg white’ like

If you’re tracking your fluid, and you notice it’s either wet / watery, or like egg white, this is the time to start having regular sex as this time = your most fertile!

This is when ovulation is about to happen.

Basal body temperature - BBT

BBT is another method of tracking your body's natural signs, although this may not be as useful for those with irregular cycles. It works by tracking the body's temperature when at rest (first thing in the morning).

During the first half of your cycle - the follicular phase - BBT usually sits around 36.1 - 36.6 degrees C. After ovulation there is a rise of 0.3-0.6 degrees C due to the secretion of progesterone. The temperature then remains higher until menstruation takes place. Occasionally you may see a dip in temperature before ovulation but not always, so this is not something to rely on.

Tips for BBT tracking:

  • use a digital thermometer that is really accurate to 0.01C.

  • test it first thing in the morning before you get out of bed.

  • use the same thermometer, and take it at the same time.

  • it is usually relatively stable but can be affected by lack of sleep, therefore, if you've had a really bad night of disturbed sleep, you cannot rely on the following mornings reading.

You're looking for a general pattern therefore you may need to monitor your BBT for a number of months to get a consensus of what your temperature does. Also, it is really important to realise that because the BBT rise comes after ovulation, you may miss your fertile window. This is why, when you can identify a pattern it will help you to time when your fertile period is. This is usually 3-4 days before rise, and 1-2 days after rise.


So, what is the best combination of tracking methods?

Tracking your cervical fluid, alongside monitoring your BBT so that you may have an indicator when ovulation has occurred, is going to give most people a really good idea of when their fertile period is. Using OPKs, in addition to these methods, may give you more reassurance that you're timing it correctly, but as explained above, they are not always the best method.


  • Look for stretchy egg white like mucus (happens BEFORE ovulation)

  • Basal body temperature - dips just before ovulation (may be seen) and rises AFTER.

  • You may also notice that your sexual desire may also increase around ovulation, so if you’re feeling more up for it that may be another sign!!

4 views0 comments


bottom of page