To prevent pregnancy, women can keep track of their menstrual cycles and abstain from unprotected vaginal intercourse during their peak fertile times. The methods you can use to do this are called fertility awareness-based methods(FAMs).
One way that women track their fertility patterns is called the temperature method.
Some women also track their temperature when trying to get pregnant to know when they should have unprotected vaginal intercourse.
Your body temperature is lower during the first part of your cycle. It usually rises slightly after ovulation when an egg is released. Your body temperature stays elevated for the rest of your cycle. It falls again just before your next period. Tracking your temperature every day can help you know when you ovulate. To prevent pregnancy, you will not have unprotected vaginal intercourse until three days after you ovulate each cycle.
You will need to chart your basal body temperature (BBT) every day. BBT is the temperature of the body when it is completely at rest. It varies slightly from person to person. Before ovulation, 96 to 98°F is normal for most women. After ovulation, 97 to 99°F is normal.
The changes will be in fractions of a degree from 1/10 to 1/2 a degree. So it's best to get a special, large-scale thermometer that only registers 96 to 100°F. It will be much easier to read. You can buy a basal thermometer for about $10 at most drugstores. Some basal thermometers are to be used in the mouth and some are to be used in the rectum. Rectal thermometers are generally more reliable. Whatever you choose, be sure to take your temperature the same way every day.
Taking Your Temperature
Take your temperature every morning as soon as you wake up. Do it before getting out of bed, talking, eating, drinking, having sex, or smoking. Keep the thermometer in place for five full minutes. Read it to within 1/10 of a degree. Record the reading.
Charting Your Temperature Pattern
You must record every reading. You can get charts from your health care provider
or women's health center. As each day's reading is put on the chart, you will begin to see a pattern. The rise in your temperature may be sudden, gradual, or in steps. The pattern may vary from cycle to cycle.
Your BBT may change when you are upset or don't get enough sleep. Illness, stress, jet lag, and smoking may also affect your body temperature. So can drinking more than you're used to or using an electric blanket. Putting these kinds of events on your chart can help you understand the pattern.
At first, you should have help to read your chart. A doctor, nurse, or family planning specialist can do that for you. In time, you'll have the confidence to use the chart by yourself. Be sure to chart at least three months before relying on this method.
Safe Days Using the Temperature Method
The safe days are those that are not fertile days. They are safe for unprotected vaginal intercourse if you are trying to prevent pregnancy. They begin after the temperature rise has lasted for at least three days. They end when the temperature drops just before your next period begins.
The temperature method is quite good at telling when ovulation has happened. But it can't predict when it will happen. So, you have to make sure that sperm is not waiting in your body when it does happen. It is best to treat as unsafe all the days of the first part of your cycle. This is from the start of your period to the start of the fourth day of your next rise in temperature. You can combine BBT with another method to try to predict when ovulation will happen. This can increase the number of your safe days.
After a while, you may become sure that you can tell what days are safe. If so, you may not have to take your temperature every day. You can go without taking it from the start of your safe days to the start of your next period.
This information is not meant as a substitute for professional advice.