Knowing when you are most fertile is the best way to know when to get pregnant within your cycle. Every women is different and it’s simply not always a case that you ovulate on Day 14 (remember this is just an average), so by charting your daily basal body temperature you will start to get a good indication of your usual ovulation day.
Charting should be used in conjunction with the other methods of determining your ovulation day because while useful, it will only confirm that you have ovulated, not tell you when you are about to. However after around two months of charting you should have a good idea when the best time to get pregnant in your cycle will be.
It’s also useful for detecting luteal phase defects (when the time between ovulation and menstruation is less than 10 days).
So how do you start charting?
The first thing that you will need is a basal body thermometer. You can get those quite inexpensively at most big supermarkets or pharmacies or even online (eBay often has BBT thermometers cheap). Make sure you get a digital one as they are much easier to read.
Starting at Day 1 of your cycle (the first day of your period), take your temperature first thing in the morning at the same time before you get out of bed. You can either temp orally or vaginally – it’s up to you whichever you prefer.
Record it on a notepad and fill in your chart. You can either print out BBT chart’s here (download blank BBT chart (pdf)) or use an online ovulation calculator like Fertility Friend and enter your temperatures in there so it does the calculations for you.
As you approach ovulation you should notice any changes in your cervical fluid to determine if you are becoming fertile. You can note these on your chart as well. Often you may find that your peak cervical mucus day is actually a day or two before you ovulate rather then the day of.
Once you have released an egg you’ll notice that your temperature will increase, often by around 0.5 to 1 degree and be higher than your previous temps of that cycle. If your temperature remains high for at least three temperatures then you can safely confirm ovulation has taken place.
The day BEFORE the rise is your ovulation day.
Draw a cover-line to distinguish your high and low temps so you can easily see your charting pattern.
The reason for the increase in temperature’s is that the body releases progesterone in the second half of your cycle which warms the body by around half a degree waiting for the impending pregnancy. If you are not pregnant, the progesterone drops and estrogen takes over and your cycle starts all over again.
There are many variations on what constitutes a ‘perfect’ chart and many women notice erratic temperatures, fall back temperatures, a dip before the rise and other out of place temperatures while they are charting. They are all normal and won’t stop you getting pregnant.
Keep charting throughout the rest of your cycle as often times you may determine if you are pregnant or not from what your chart does. If the temps remain high past your usual cycle length then it is a good chance that you might be pregnant. If you notice that your temps fall then it’s likely that your period is on its way either later that day or the next day.
After a few cycles it’s likely that you’ll know your body very well and you’ll be able to determine when to get pregnant in your cycle just by looking at your previous charts.