Blackmores How to chart your cycle

How to chart your cycle

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Learn to pinpoint the best days to conceive a baby with these tried and tested techniques

If you’re looking to get pregnant, there’s a lot to be said for knowing when you’re most likely to conceive – the science of ovulation timing is more complex than many first think. 

Here are three of the most common cycle-charting techniques. 

What is the ‘fertile window’?

There are roughly six days within your menstrual cycle in which you’re fertile and able to conceive. This window includes the five days leading up to your ovaries releasing an egg, a process called ovulation, as well as the sixth day when the egg is released into your fallopian tubes. 

The fertile window reflects both the five-day lifespan of sperm, and the 24-hour lifespan of your ovum. 

Chances of getting pregnant

Almost 0% During the days outside of the fertile window
Around 10% Five days prior to ovulation
Around 16% Three days prior to, and including, ovulation
Between 27- 33% Three days prior to, and including, ovulation
Almost 0% Between 12 and 24 hours after ovulation

Method 1. - Track your cycle

  • For a few menstrual cycles, keep track of the overall length of your cycle. Day 1 is the first day of your period; the last day is the day before your next period begins
  • Note the lengths of each cycle and work out the average length of your cycle
  • Subtract 18 days from the length of your shortest cycle (eg. 27 days). This is the first day of your cycle you’re likely to be fertile
  • Subtract 11 days from the length of your longest cycle (eg. 32 days) This the last day of your cycle in which you’re likely to be fertile
  • Your fertile window is the time that falls between your first and last fertile days
Online ovulation calculators use a more simple matrix, so may be less accurate, but for a general clue as to when your fertile window falls, check out this calculator by WebMD

Method 2. – Take your temperature

Your body temperature rests at different points before and after ovulation (the difference can be less than a degree), so tracking what’s called your body basal temperature (BBT) each day will help you stay on top of when it is you’re about to ovulate or have already ovulated.

Here’s how it works :

  • Using a basal body thermometer (available from chemists for under $20), check your temperature first thing in the morning before you get out of bed – this is because going to the bathroom and other activities, such as drinking tea, can change your body temperature slightly). Do a reading by placing the thermometer under your tongue
  • Chart your temperature for around two cycles to get an idea of your pattern
  • Your temperature will remain low from the start of your period until the end of ovulation. When your reading is higher for three days straight, this means ovulation is over and you’ve entered the infertile stage of your cycle
  • Use your knowledge of the three straight days of higher temperature to know when your ovulation phase is over
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Method 3. – Check your mucus

In the lead up to ovulation, the viscosity and colour of your cervical mucus (the fluid that ends up in your underwear after travelling through the vagina) changes – this is to assist the sperm in reaching your egg.

 To note mucus changes:

  • Clean your hands, and with a tissue or your fingers, check for mucus inside the vagina (about an inch or so up from your labia). You can also examine this mucus on toilet paper after you’ve passed urine
  • If your vagina is mostly dry and there’s very little mucus, this is considered ‘phase one’: the infertile phase
  • When more mucus begins to appear and its sticky and/or stretchy, you’re entering ‘phase two’: the fertile stage of your cycle. Early on, this will be a little creamy, but then, as you become highly fertile, the mucus will gather more water content and become stretchier – it will resemble an egg white
  • ‘Phase three’, after ovulation, begins when the mucus becomes thick and white. When this occurs, your fertile window has closed until the next menstrual cycle begins