What is BBT - Basal Body Temperature? - MCN Network - Find Help Near You
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Basal Body Temperature?

The body’s lowest temperature at rest, typically measured in the morning after several hours of uninterrupted sleep and before any physical activity. BBT is influenced by hormonal changes, particularly the rise in progesterone after ovulation, which causes a slight increase in temperature. Tracking BBT over the menstrual cycle can help identify the timing of ovulation and establish fertility patterns.

Key Features:

  • Measurement:
    • BBT is measured using a basal body thermometer, which is more sensitive and accurate than a regular thermometer.
    • Temperature is taken orally, vaginally, or rectally upon waking, before any physical activity, and ideally at the same time each day.
  • Variations:
    • BBT typically ranges from 97.0°F (36.1°C) to 97.7°F (36.5°C) before ovulation and rises by about 0.5°F (0.3°C) after ovulation due to the release of progesterone.
    • The rise in BBT persists until the onset of menstruation, signaling the end of the luteal phase and the beginning of a new menstrual cycle.
  • Fertility Tracking:
    • Charting BBT over several menstrual cycles can help identify the pattern of temperature changes and predict ovulation.
    • The fertile window is typically identified as the days leading up to and including the day of ovulation, when BBT rises.
  • Applications:
    • Used in fertility awareness-based methods (FABMs) of contraception and natural family planning to identify fertile and infertile days.
    • Can aid in timing intercourse for couples trying to conceive by targeting the most fertile days of the menstrual cycle.
  • Limitations:
    • BBT is retrospective and confirms ovulation after it has occurred, rather than predicting it in real-time.
    • Factors such as illness, poor sleep, alcohol consumption, and stress can affect BBT measurements and may obscure fertility patterns.
    • Not a standalone method of contraception or fertility prediction and is often used in combination with other fertility awareness methods or assisted reproductive technologies.

 

Online References:

  • Mayo Clinic: Provides information on basal body temperature tracking, its purpose, how to measure it, and its role in fertility awareness.
  • American Pregnancy Association: Offers guidance on how to track basal body temperature, interpret patterns, and use it in fertility planning.
  • Verywell Family: Provides an overview of basal body temperature charting, its benefits, and how to interpret temperature patterns.