In order to conceive a child or to avoid pregnancy through natural family planning methods, women may monitor their menstrual cycles to predict when ovulation, the release of a mature egg from the ovary, may occur. Although ovulation may take place at any time in the cycle, there are generally certain signs that precede it. The connection between basal body temperature and ovulation, for example, is that the reading will rise slightly just prior to the release of the egg.
Basal body temperature is the temperature of the body at rest. Since activity of any type can affect this reading, the best time to take the temperature is in the morning prior to getting out of bed. To chart basal body temperature and ovulation properly, a thermometer that can take readings to 0.10 (1/10th) of a degree is needed. Either a special basal thermometer or a regular digital one that meets this specification can be used.
Prior to ovulation, a woman's readings may range from a low temperature of 96 degrees Fahrenheit (35.5 degrees Celsius) to a high temperature of 98 degrees Fahrenheit (36.6 degrees Celsius.) This is lower than the generally known body temperature standard of 98.6 Fahrenheit (37 degrees Celsius), but this is to be expected because the body is at rest. Low basal body temperature is typically not a cause for concern unless readings are frequently below 95 degrees Fahrenheit (35 degrees Celsius.)
Approximately halfway through her menstrual cycle, a woman should notice a very slight increase in temperature. This increase may be as little as 0.10 of a degree. Careful monitoring in the days following the rise in the basal reading will indicate whether it was due to ovulation or not. If ovulation did occur, the basal body temperature will not go back down until after the woman has her menstrual period.
Basal body temperature and ovulation should be plotted on a chart to monitor patterns. The bottom of the chart should have lines for each day of the woman's menstrual cycle, with the first day of her period counted as day one. The side of the chart should have lines for temperature readings, with one space for each 0.10 of a degree. A dot should be placed where the lines intersect for the appropriate day and temperature, with lines drawn from dot to dot to make rises and dips more obvious.
Pregnancy is most likely to occur in the three days before ovulation, the day of the egg release and the three following days. Several months of charting may be necessary for a woman to become comfortable with predicting ovulation using this method. Women with irregular periods and those whose charting yields unpredictable results should choose another method of fertility awareness, particularly if they hope to avoid pregnancy.
