| The Symptothermal Method -- Getting
Started |
This on-line document
explains how a woman can learn to identify her fertility signs and
symptoms. Women wishing to use the Symptothermal Method to avoid or
to achieve a pregnancy are advised to contact a qualified Natural
Family Instructor.
Basal Body
Temperature (BBT)
The BBT is the
body temperature of a healthy person on awakening. The BBT rises
under the influence of progesterone. Most ovulatory cycles
demonstrate a biphasic BBT pattern: lower in the first part of the
cycle, rising to a higher level beginning around the time of
ovulation, and remaining at the higher level for the rest of the
cycle. By taking her temperature on a chart each day of her
menstrual cycle, a woman can retrospectively identify when she may
have ovulated. However, because the BBT does not give adequate
advance warning of ovulation, it cannot be used to identify the
start of the fertile time. Therefore, it is of limited use for a
woman who wants to achieve pregnancy.
Figure 4
illustrates the BBT variations during a model menstrual cycle of 28
days. In reality, the BBT may rise more suddenly or more gradually.
The typical pattern of a lower temperature before ovulation,
followed by a higher temperature immediately before, during, and
after ovulation, can be disrupted by illness, stress, travel, or
interrupted sleep.
Figure 4. Temperature variations during a menstrual
cycle
Use the BBT to
determine the postovulatory infertile time:
- Take your
BBT every morning at the same time before getting out of bed
(after at least 3 hours of sleep). A special calibrated
thermometer makes temperature reading easier. Take the BBT orally,
rectally, or vaginally, but take it at the same site each day so
changes in BBT can be detected accurately.
- Record your
BBT readings daily on a special NFP chart (similar to
that in Figure 4). Connect the dots for each day so a line
connects dots from day 2 to day 3, and so on.
- Your
temperature will probably rise at least 0.4° F around the time of
ovulation and remain elevated until the next menses begins. Your
actual temperature and maximum temperature are not important, just
the rise over the baseline (preovulatory) temperatures.
- If you have
3 days of continuous temperature rise following 6 lower
temperatures, you have ovulated and your postovulatory infertile
time has begun. To see the baseline and rise clearly on the chart,
draw a line just above (0.1 degree line) the lower (preovulatory)
temperatures. When you record 3 continuous temperatures above this
line and the last temperature is 0.4 degrees higher than this
line, your postovulatory infertile time has begun.
- If you
cannot detect a sustained rise in BBT, you may not have ovulated
in that cycle. A true postovulatory BBT rise usually persists 10
days or longer.
- Some woman
notice a temperature drop about 12 to 24 hours before it begins to
rise after ovulation, whereas others have no drop in temperature
at all. A drop in your BBT probably means ovulation will occur the
next day.
- To
conceive. It is not possible to predict fertile days using
BBT. By the time the rise is detected, you are probably in the
infertile phase of your menstrual cycle and have missed the
opportunity to become pregnant. A biphasic temperature pattern,
however, can let you know you are probably ovulating
normally.
- To avoid
pregnancy. Because the ovulation may occur as early as day 7
of the menstrual cycle, assume you may be fertile from just after
menses (if your cycles are no less than 25 days in length) until
your temperature has remained elevated for at least 3 consecutive
days. The most effective way to use BBT charting when avoiding
pregnancy is to avoid intercourse all through the first part of
your cycle,until the temperature rise indicates you have ovulated.
Note:
Because BBT does not provide information about the beginning of the
fertile time, it is rarely used as the only fertility indicator by a
woman who is using NFP.
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