Basal body temperature is a person's temperature taken when they first wake up in the morning (or after their longest sleep period of the day). In women, ovulation will trigger a rise in BBT between 0.3 and 0.9 °C (0.5 and 1.6 °F) that lasts approximately until the next menstruation. Sixty percent of the time, ovulation happens the day before the temperature rise. The other forty percent of the time, ovulation may happen a few days in either direction.
Some women feel that the addition of a device, even a thermometer, takes away from the personal and self-referral experience of natural birth control. Other women enjoy the scientific confirmation of their mucus and cervical observations.
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What to Look for on Your Basal Body Temperature Chart
During the first part of a woman's menstrual cycle basal body temperatures will be lower. The first half of your menstrual cycle is called the follicular phase. Right before ovulation you will have a slight drop in temperature followed by a sharp rise in temperature. Not all women will have a drop in temperature before ovulation but if you notice your temperature drop, you should start having intercourse then.
Around the time of ovulation, you will see a rise in temperature, By the time you notice this rise in temperature, you have already ovulated. That is why charting works best when done for a few months. What you are looking for is a rise in temperature of about 0.4 degrees or more. If you have ovulated your temperature will remain higher. If your temperature remains higher for three days or more, then you can assume you have ovulated.
CHARTING YOUR BBT
Here are general recommendations when charting your Basal Body Temperature:
- Buy a basal body temperature thermometer (glass thermometers are best).
- Start charting on the first day of your menstrual period.
- Shake down the thermometer before you go to bed. Place it on a table neat the bed.
- Take your temperature for five minutes each morning right after waking up. Do this before getting out of bed, smoking, eating, or drinking, Any activity may raise your temperature.
- Record your temperature on the chart by placing a black dot on the temperature line in the correct date column.
- Draw a line between yesterday's temperature dot and today's dot.
- Mark days you have sex by circling the dot.
- Change the temperature dot to a star if there is some other reason your temperature might change: a cold, fever, a restless night, or medicine like aspirin or paracetamol, which are fever reducers.
- Start a new chart the day your period begins. Mark the days of your period with an "X".
Put a dot on a graph on the spot corresponding to each day's temperature. Join the dots of consecutive days. If you do not take your temperature one day, do not join the dots across that day. Also write out the temperature numerically in the space provided.
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On this chart, ovulation is most likely to occur on day 14 (with 1-2 days variation).
Every woman's chart is different. Also in different cycles you may have a different picture. Ovulation times vary depending on stress levels, diet, exercise, environment, sexual activity, medication, illness and other factors. To find out more, you can check out Female Fertility Test.
