Basal body temperature
| Basal body temperature | |
|---|---|
| Background | |
| Type | Fertility awareness |
| First use | 1930s |
| Failure rates (first year) | |
| Perfect use | Unknown% |
| Typical use | Unknown% |
| Usage | |
| Reversibility | Immediate |
| User reminders | Dependent upon strict user adherence to methodology |
| Clinic review | None |
| Advantages and disadvantages | |
| STI protection | No |
| Period advantages | Prediction |
| Weight gain | No |
| Benefits | No side effects, can aid pregnancy achievement |
Basal body temperature (BBT or BTP) is the lowest body temperature attained during rest (usually during sleep). It is usually estimated by a temperature measurement immediately after awakening and before any physical activity has been undertaken. This will lead to a somewhat higher value than the true BBT.
In women, ovulation causes a sustained increase of at least 0.2 °C (0.4 °F) in BBT. Monitoring BBTs is one way of estimating the day of ovulation. The tendency of a woman to have lower temperatures before ovulation, and higher temperatures afterwards, is known as a biphasic temperature pattern. Charting this pattern may be used as a component of fertility awareness. The BBT of men is comparable to the BBT of women in their follicular phase.