The basal body temperature (BBT) is a person's at-rest
temperature.
Natural cyclic changes in female hormones usually
cause a woman's basal body temperature to go down slightly just before an egg
is released (ovulation) and then go up sharply 24 hours after ovulation. By
carefully measuring BBT every morning before getting out of bed and recording
it on a chart, many women are able to estimate when they are ovulating. This
helps pinpoint when a woman is most and least likely to become pregnant.
The change in your body temperature is very slight, so you need to use a
special thermometer to measure it. You can use a regular digital thermometer,
or you can buy a basal thermometer. A basal thermometer shows you the
temperature in tenths of a degree. This allows you to note tiny changes in body
heat.
Keeping track of basal body temperature may be helpful for
women trying to get pregnant or trying to avoid pregnancy. It is one of several
fertility awareness or natural family planning methods of birth control.
- Having sex during the 5 days before and the day
of ovulation increases your chances of becoming pregnant.
- Avoiding
sex up to and until several days after you have ovulated may help you prevent
pregnancy, because the human egg is typically fertile for only 12 to 24 hours
after ovulation.
Basal body temperature charting is done at home and is
inexpensive. But to get an accurate record, a woman needs to track her
temperature every day for several months. Women who work varying shifts or who
have irregular menstrual cycles may have difficulty getting a useful basal body
temperature measure.
