The temperature method
One of the changes that ordinarily take place in a woman's body as part of her menstrual pattern is that her body temperature is lower during the first part of the cycle. In most women it usually rises slightly with ovulation and remains up during the second part until just before her next period. Recording each day's temperature helps to indicate when ovulation has occurred. The temperature method requires charting your basal body temperature (BBT), the temperature your body registers when you're completely at rest. BBT varies slightly from person to person. For most women, 96 to 98 degrees Fahrenheit taken orally is considered normal before ovulation and 97 to 99 after. The changes are small fractions from 1/10 to 1/2 degree. So it's best to get a special, large-scale, easy-to-read thermometer that registers only from 96 to 100 degrees. A rectal or oral basal temperature thermometer can be bought in most drug stores for about $10. Generally, rectal readings are more reliable. But whichever you choose, take your temperature the same way every day. As each day's temperature is plotted on the graph, you will learn to recognize your own pattern. Your temperature rise may be sudden, gradual, or in steps. The pattern may vary from cycle to cycle. You must also realize that your BBT can be influenced by physical or emotional upsets or even lack of sleep. In addition, illness, emotional distress, jet lag, disturbed sleep, smoking, drinking an unaccustomed amount of alcohol the night before, and using an electric blanket may affect your body temperature. Be sure to chart your temperature for at least three months before relying on this method. After the temperature rise has lasted for at least three days, you can assume that your ovulation is over and the safe days have begun. They will last until the temperature drop that usually comes just before your next menstrual period. The temperature method is quite accurate in detecting when ovulation has occurred, but can't predict when it's about to happen. When you become confident about using your BBT to determine your safe days, you may not need to take your temperature between the start of the infertile time and the beginning of your next menstrual period.