Q: What could low basal body temperatures (BBT) mean?
A: The BBT temperature is just an average. Normal BBT temperatures are between 97.7 and 98.2 degrees Fahrenheit. Many women have lower-than-average temperatures. But, if your temperatures are lower on a consistent basis, and if you have fertility problems, you may want to have your thyroid checked. A low temperature is sometimes a sign of a low thyroid (hypothyroid), which can cause some fertility problems such as anovulation.
Fertility Charting - Basal Body Temperature BBT
Thyroid Disease and Pregnancy