My knowledge on this all comes from reading Toni Wechsler’s “Take Charge of Your Fertility” book and I recommend you have a read. It’s the basis of the algorithm Fertility Friend uses to predict ovulation. The main focus of TCOYF is charting basal body temperature. Monitoring cervical mucus (CM) and cervix position are secondary and using ovulation using OPKs are considered not much help at all. I’ll go through what I learned about each in turn and maybe some of the other ladies can share their own experience.
Temperature rises by about 0.25 to 0.5 oC after you have ovulated. This is due to the release of progesterone by the corpus luteum (the follicle that released the egg) which basically sending this signal for 12-16 days after the egg is released – this is known as the luteal phase – this is long enough for the fertilised egg to implant which in turn release HCG (the hormone detected by pregnancy tests) – its job is to tell the corpus luteum to continue to make progesterone until the placenta takes over.
So anyway – the day after ovulation, temperature increases and TCOYF will tell you that 18 high temperatures = pregnancy (not that any of us ever wait that long). FF will require 3 temps higher than your coverline (I’ll explain that in a minute) to decide you’ve ovulated.
The coverline is set at the highest temp of your previous 5-6 days (it uses a rolling window to figure out if your higher temp is high enough).
Things that affect temperature include drinking alcohol the night before, getting up late/early, disturbed sleep, illness. If you include this data in FF it will take account of it (generally by marking an unfilled circle on your chart rather than a solid one).
So how to temp (I’ll describe my personal experience later so as not to confuse things) – generally it is supposed to be the first thing you do when you wake up – turn off the alarm, put the thermometer in and wait. If you wake early and won’t get 2-3 hours sleep before your normal wake up time do it then and mark the time change on your chart. If you wake up late just mark that on your chart too. Don’t take multiple temps, it will only confuse the issue.
As for thermometer – TCOYF recommends a basal thermometer, digital one with only one decimal place (if yours has two, round it up or down accordingly). Some people prefer an analogue (glass) thermometer since they don’t beep but you should always shake it down the night before.
Things temping can also indicate are an inplantation dip (usually around 5-10DPO) and a triphasic chart which looks like you’ve ov’d again because you get 3 or more days of an even higher temp – these can both be indicators of pregnancy or not mean anything at all.
Personally I started temping mid way through my first cycle off the pill (I got to CD30-odd and no sign of AF so I gave it a go). It turned out I had already ov’d but I didn’t know that until much later. My first experience of it temp fluctuation was one day it plummeted and later that day AF arrived.
I have found that my BBT doesn’t vary much no matter when I wake, I used to go sit on the loo and take my temp, completely flouting the no movement rule – it worked fine. I also used a bog standard fever thermometer from the pharmacy – it was fine too. Alcohol affected me, but only if I had at least two glasses of wine the night before. Otherwise, my temps were always in my pre-ov range of below 36.4 before ov and above 36.6 after ov. You’ll learn what works for you.
One more thing, if you sleep with your mouth open you may find you need to temp vaginally (it’s exactly as it sou