Fertility Awareness-Based Methods: Another Option for Family Planning

Stephen R. Pallone, MD; George R. Bergus, MD

Disclosures

J Am Board Fam Med. 2009;22(2):147-157. 

In This Article

Basal Body Termperature

Basal body temperature (BBT) elevation, another older method, retrospectively identifies fertility. The luteinizing hormone surge, which stimulates ovulation, is associated with a 0.5- to 1°F- (0.9- to 1.8°C-) rise in BBT measured with highly standardized methods. BBT can be taken orally, vaginally, or rectally with a sensitive thermometer; the same site should be used daily. BBT is measured on awakening at approximately the same time every morning, before getting out of bed or doing any other activity. At least 6 hours of uninterrupted sleep the preceding night is necessary for accurate measurement. BBT remains elevated throughout the luteal phase secondary to higher progesterone levels. The woman is assumed to have ovulated after observing 3 consecutive days of temperature elevation. Pregnancy is avoided by abstaining from the beginning of menstruation until 3 to 4 days after the rise in BBT. All subsequent days until the beginning of her next menses are considered infertile.[63]

Because sperm survive 5 days, BBT alone does not predict ovulation far enough in advance to identify all the potentially fertile days; it predicts only peak fertility, so thus the need to abstain from the beginning of menstruation. Many other factors also limit the use of BBT. Some women ovulate without a clear rise in BBT.[22] Alcohol consumption, late nights or oversleeping, disrupted sleep, travel, time zone differences, holidays, shift work, stress, illness, gynecologic disorders and medications can all lead to inaccurate basal temperature measurement.[22] Moreover, the biphasic shift of BBT has been found to vary up to 1 day before and 3 days after actual ovulation.[22,63] Extensive reviews of BBT have been conducted elsewhere.[4,23,24]

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