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basal body temperature
基礎体温を毎朝測っている。
I measure my basal body temperature every morning.
基礎体温の変化で体調を把握できる。
You can understand your physical condition through changes in basal body temperature.
基礎体温が上がり始めたため妊娠に気づいた。
Her basal body temperature started rising and she noticed she was pregnant.