Monitoring ovulation has never been an exact science and recent research has shown it’s even less so than previously thought.
Many women ovulate or have the potential to ovulate more than once per month, so having intercourse at other times besides your predicted ovulation date could lead to conception. To further complicate the issue, one study found “in only about 30% of women is the fertile window entirely between days 10 and 17… women can reach their fertile window earlier and others much later. Women should be advised that the timing of their fertile window can be highly unpredictable,
even if their cycles are usually regular.” (1)
When I tried taking my temperature to see when I was ovulating I found my temperature fluctuated so much I really
couldn’t find a pattern. It was also difficult for me to remember to take my temperature at the same time every day. The other
problem is that by the time it goes up, you may have already ovulated. Another study found “among healthy women trying to conceive, nearly all
pregnancies can be attributed to intercourse during a six-day period ending on the day of ovulation”(2). So you can see if you wait for your temperature to go
up, you've pretty much missed your fertile window.
I’ve talked with a number of doctors about the “temperature” method and they weren’t crazy about it.
My first fertility doctor came out and said “it doesn’t work”. One way you could use the temperature method is to establish a pattern of
your ovulation cycle day just so you can start planning intercourse well before then.
For that reason, I have included the BBT method below.
BBT Charting To Establish A Pattern
1. Begin taking your temperature on the first day of your cycle (see above)
2. Take it the same time every day before you get out of bed in the morning and before you eat or drink anything
(you will need to keep a thermometer and chart next to your bed and you may need to set an alarm)
3. Take your temperature orally using a digital thermometer (or check with your local drugstore for a special BBT thermometer)
4. Using a piece of graph paper (or a chart), record your temperature each day with temperature on the left (vertical)
with each square representing .1 degree. Put the day on the bottom of the graph (horizontal)
5. After ovulation, your temperature should go up about .1 to .4 degrees. Although this is a small change, it is significant.
Your temperature may stay elevated until you get your period again (pregnancy will also keep your temperature elevated.)
6. There might be a very slight dip in temperature immediately preceding ovulation
If you go back and analyze the chart after a month or two, you should see that the “follicular” temperatures (those before ovulation) should be lower and
the “luteal” (after ovulation) temperatures should be higher. Again, there are pitfalls to this method because there are things unrelated to
ovulation and pregnancy that can affect your BBT. Everything from illness, lack of sleep, too much heat or heated blankets, exhaustion
and alcohol can all affect your temperature.
(1)Wilcox AJ, Dunson D, Baird DD., The timing of the "fertile window" in the menstrual cycle: day specific estimates from a prospective study,
BMJ. 2000 Nov 18;321(7271):1259-62.
(2)Wilcox AJ, Weinberg CR, Baird DD,Timing of sexual intercourse in relation to ovulation. Effects on the probability of
conception, survival of the pregnancy, and sex of the baby, N Engl J Med. 1995 Dec 7;333(23):1517-21.
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