Basal Body Temperature Changes During Menstrual Cycle - Obstetrics and Gynecology

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Understanding the changes in basal body temperature (BBT) during the menstrual cycle is crucial for women who are tracking their fertility or experiencing irregular cycles. The menstrual cycle is typically divided into two main phases: the follicular phase and the luteal phase. Each phase is characterized by distinct hormonal changes that influence BBT.

During the follicular phase, which begins on the first day of menstruation and lasts until ovulation, estrogen levels rise. This increase in estrogen generally keeps BBT lower, typically ranging from about 36.1°C to 36.4°C (97°F to 97.5°F). As ovulation approaches, there is a surge in luteinizing hormone (LH), which triggers the release of an egg from the ovary. This event usually occurs around the midpoint of the cycle.

After ovulation, the luteal phase begins. The corpus luteum, which forms from the remnants of the follicle that released the egg, produces progesterone. Progesterone is responsible for raising BBT, often resulting in a temperature increase of about 0.2°C to 0.5°C (0.4°F to 0.9°F). This elevated temperature typically lasts until the onset of menstruation. If pregnancy does not occur, progesterone levels drop, leading to a decrease in BBT, which is often observed just before or at the start of menstruation.

In your case, you mentioned taking ovulation medication for five days and observing a BBT of around 36.8°C just before your period. This temperature is indeed higher than the typical follicular phase temperatures, suggesting that ovulation may have occurred. However, it is not uncommon for BBT to remain elevated or not drop significantly during menstruation, especially if hormonal medications are involved. These medications can influence the hormonal balance and, consequently, the expected temperature patterns.

Regarding your observation that your BBT remained around 36.6°C to 36.7°C during your period, this can happen for several reasons. First, hormonal fluctuations due to the medication may prevent the typical drop in temperature that usually accompanies menstruation. Additionally, individual variations in hormonal responses can lead to different BBT patterns. Some women may experience a more gradual decline in temperature rather than a sharp drop.

As for the timing of measuring BBT, it is generally recommended to take your temperature first thing in the morning, before getting out of bed, and at the same time each day for consistency. This practice helps to ensure that the readings are not influenced by daily activities or other factors that can temporarily alter body temperature.

In summary, while it is common for BBT to drop at the onset of menstruation, various factors, including hormonal medications and individual physiological responses, can lead to variations in this pattern. If you have concerns about your menstrual cycle or BBT patterns, it may be beneficial to consult with a healthcare provider who can offer personalized insights and guidance based on your specific situation.