Today I’ll talk a little about temperature charting. I’ve linked above an image of last month’s chart from fertilityfriend. At the top you see the date, the bottom you see the Cycle Day number. I usually end up only paying attention to the Cycle day number. The CM line stands for Cervical Mucus. The Test line shows the many pregnancy tests I took that were all negative. And the Meds Line marks FE on the days I took the femara. You can see a few other things here. The dotted line on Day 4 means I didn’t record a temperature that day. Open circles usually mean that I slept too long. Fertilityfriend gives open circles anytime you enter something that may mean the accuracy of the temperature is off. Sleeping in, getting up too early, and not sleeping well (marking sleep deprivation) are all examples of cases when the temperature accuracy may be questionable. The red crosshairs marks where ovulation most likely occured. I take my temperature as soon as I wake up in the morning before getting out of the bed. This is important. Your body temperature may change once you get up. So to accurately get your basal body temperature, it has to be as soon as you wake up before getting out of the bed.
So, that’s background on what you see. Why does a woman’s temperature change after ovulation? Progesterone in the bloodstream is the key to this chart. Early in a cycle, estrogen is the dominant hormone (this is the follicular phase). After ovulation, the Corpus Luteum (what remains of the follicle after it releases the egg) takes over hormone production causing progesterone to rise, and estrogen declines (also known as the luteal phase). Progesterone will remain high until right before menstruation, where it will drop and estrogen will take back over. If pregnant, the corpus luteum will continue with progesterone production through the first trimester, at which time the placenta takes over.
Progesterone is what causes your temperature to rise. So, temperatures should be relatively low, then right after ovulation, your temperature will rise due to the rise in progesterone. My chart I linked above shows this temperature shift. I’ve found that most anything can affect the BBT. If I wear warmer PJ’s, then my bbt may be slightly higher. If you sleep with your mouth open, it may be off a little bit. And so on. But you can see in the chart I included here, that while it is not perfect, and the conditions weren’t always ideal, you can still see the temperature shift.
Charting is good to see if you are ovulating. But, ovulation is confirmed after the fact, so it is not great for timing things just right. Fertilityfriend won’t confirm ovulation until you have 3 consecutive days of high temperatures. FF will also use the other signs, such as cervical mucus, to determine when you ovulated. It takes all of the information you give it and tries to cross-check everything. There is other charting software out there, I’m sure. You could also do this by hand, but I find it very easy to enter into the website every morning.
I also like to chart because that helps me figure out whether I could be pregnant or not. Last month, when my temp dropped, I had a hint that the cycle probably didn’t work out. When it continued to go down, I pretty much knew that it was over at that point. Also, while a woman may not ovulate on the same day every month, usually her luteal phase is pretty constant. I know if my luteal phase goes beyond 14 days, then something’s up! Most pregnancy tests are reliable at 14 days past ovulation, so it helps with timing when to test as well. So, while I don’t have to chart my temperature according to my RE I continue to do so anyway, because it gives me some extra cross-checking points.
ABCs of Basal Body Temperature Charting
Fertility Plus: Hormone Levels and Fertility Bloodwork