Average Failure Rate: 16%
The sympto-thermal method of natural birth control involves determining the few days out of a woman's menstrual cycles when conception can occur, and then avoiding sexual intercourse on those days. This method involves determining this fertile time in two ways: based on a woman's basal body temperature (it rises after ovulation) and by recording other fertility cues (such as mood and cervical secretions). The name "sympto-thermal" method, comes from body cues (i.e. symptoms) and a woman's temperature (i.e. thermal or thermometer).
How It Works: The Thermo Part
The sympto-thermal method requires that a woman
take her temperature every morning before she gets out of bed
and record the reading. Depending on where she is in her menstrual
cycle, there will be slight variations in her temperature. These
variations are most easily measured with a special thermometer
that has a range of only a few degrees, known as a
Before ovulation, the temperature is likely to be between 97.2
and 97.4 degrees F. After ovulation, it will rise by at least 0.5 degrees and
is often above 98 degrees F. When the temperature stays elevated for
at least three days, a woman may assume she has already ovulated.
Intercourse for the rest of the cycle will not result in pregnancy.
To determine the infertile time before ovulation, a woman needs
to look at her pattern of previous cycles. Her last "safe"
day is one week before the earliest recorded day of temperature
rise, or 5 days after the first day of her period.
How It Works: The Sympto Part
By recording other cyclic symptoms,
in addition to basal temperatures, the infertile time before ovulation
can be more accurately predicted (see Ovulation Method).
Cervical mucus and firmness, mid-cycle cramping,
breast sensitivity, and mood swings are all symptoms which give
insight into the progression of a woman's cycle. With careful
monitoring, it is not difficult to predict your fertile period,
when intercourse is to be avoided. A blank NFP chart
for recording these changes is available to view, download, or print.
Intercourse during the time before
ovulation is less safe than the time after ovulation because sperm
have been known to live up to six days. For this reason, some
couples choose to have sex only after the fertile period. This
practice, known as the post-ovulatory temperature method, is the
most effective of all natural methods, with a failure
rate of only 1% among perfect users. However, it is not recommended
because it requires a very long period of abstinence.
Effectiveness of the Sympto-Thermal Method
Consider the sympto-thermal method if you are committed to following the rules strictly.
This method can be more difficult to use for women with small infants, as getting up frequently in the night can make the temperature readings less accurate.
Illness, travel, or alcohol consumption can throw off the basal temperature reading as well.
This is why it is important to use as many body signs as possible to predict ovulation for maximum efficacy.