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Instructions for recording and using the Basal Tempurature Graph

Most people believe that there is a chance for conception whenever intercourse takes place. Actually, this is not true. Conception can follow only if intercourse occurs near the time when the egg (ovum) is released by the ovary (ovulation). Obvious fertilization is impossible if there is no ovum to be fertilized. As far as we know, ovulation occurs only once in each menstrual cycle. This means that a woman has only one opportunity for conception during her cycle. The importance of determining the exact time of ovulation is therefore apparent. An individual who wishes to become pregnant may increase her chances of conception enormously by having intercourse at the time of ovulation, or on the contrary, she may decrease the chance of conception by avoiding intercourse at that time.

One simple method of determining the time of ovulation is by means of temperature graphs. Theoretically the normal temperature of a healthy individual is 98.6 degrees. Actually, there are always slight variations from this fgure. It has been found that a woman's temperature is lower during the first part of the menstrual cycle than it is during the last two weeks of the same cycle, and further, that the shift from the lower level of temperature to the higher occurs about the time of ovulation. Therefore, in many cases, it is possible to determine the time of ovulation by keeping a graphic record of each day's temperature. The variation in temperature is slight, only a few tenths of a degree, so it is essential that the temperature be taken with the utmost practical accuracy.
The temperature is to be taken precisely according to your physician's instruction; some doctors wish the temperature taken in the morning, some in the evening, some prefer mouth temperatures, some rectal temperatures. No matter what technique is used the results will be about the same. One of the best plans is as follows:

  1. 1. Take the temperature with a special "metabolic" thermometer for five minutes by the clock immediately after waking in the morning and before arising, eating, drinking, or smoking.
  2. 2. Note the temperature immediately by a dot on the graph. If the temperature so recorded differs markedly from previous readings, and particularly if it is lower than previous readings, the thermometer should be shaken down and re-inserted for an additional five minutes by the clock and the reading verified before it is recorded permanently.
  3. 3. If the temperature rises 4 to 6 tenths of a degree above the previous level and if the rise is not due to a sore throat or some other ailment, it is probable that ovulation is taking place. This is particularly likely if the temperature rise occurs about 14 days before the next period Is expected, or if the rise corresponds with a similar rise in the graph of the previous menstrual cycle. In many instances the temperature drops 2 to 4 tenths of a degree the day before it rises.
  4. 4. If the temperature is taken according to directions, and is accurately read, the time of ovulation will be indicated. Intercourse during the 24 hours following the temperature drop, or during the 24 hours following the temperature rise offers the best chance of conception in most cases.
  5. 5. It is necessary to continue recording the temperatures for at least two menstrual cycles before the graph is of much value. With a graph of two cycles at hand to provide the pattern of your own temperature curve it is usually possible to redict when the temperature will shift (ovulation). Sexual abstinence for several days before ovulation allows time for the male to store up matured sperm and probably increases the chance of fertilization. Intercourse more than once in twenty-four hours is unnecessary.
  6. 6. In order to assist your physician in interpreting the graph, it is important to make the following notations:
    1. Encircle the temperature dot on the days when intercourse occurs and write "A.M." or "P.M." as the case may be above the circle.
    2. Some women can recognize ovulation by a twinge of pain low on one side of the abdomen, or by a slight drop of vaginal bleeding. If either of these signs appear, make a note of it on the graph.
    3. Any recognized cause for fever should be noted on the chart, for example a cold, grippe, marked indigestion, or even too many cocktails.
    4. Mark the days of menstruation by an "X." It is not necessary to take the temperature during the flow. Commence a new graph for each cycle, beginning by placing an "X" at the left of the graph sheet on the line marked at the top of the graph " I."

A sample graph is shown below. Note that in the first graph there was no chance for conception because intercourse did not occur at the time of ovulation. During the next cycle the timing was better and pregnancy followed.

(References to the medical literature will be found in the J.A.M.A.. 124: 698-700, March 11, 1944. J. of Ob. & Gyn. Brit. Emp. 62: 241-252, June. 1945, Mod. Clinics of North America, 1425-1434. November. 1945.)