Ovulation and Temperature Fluctuations in Menstrual Cycles

Basal body temperature/ovulation issues?

The last menstrual cycle was 49 days.
On May 25, the first day of menstruation, ovulation was detected on day 34 with a weak positive result (temperature dropped to 36.1°C).
An ultrasound was performed that day, showing a follicle measuring 1.79 cm and a uterine lining of 0.75 cm.
On day 35, the ovulation test was strongly positive (temperature 36.14°C), and on day 36, it became weakly positive (temperature between 36.81°C and 36.90°C), maintaining this for 14 days (temperature dropped to 36.32°C).
Menstruation started on July 13 (temperature dropped to 36.24°C).
From the first day of menstruation on July 13 to day 16, the temperature ranged from 36.24°C to 36.22°C.
On day 17, ovulation was detected with a weak positive result (temperature 36.35°C - no significant drop).
An ultrasound was performed that day, showing a follicle measuring 1.70 cm and a uterine lining of 0.84 cm (the doctor said it would mature in 1 to 2 days).
On day 18, the ovulation test was negative (temperature 36.38°C) - from this day onward, all ovulation tests were negative.
On day 19, during a follow-up visit, the follicle measured 0.70 cm (temperature 36.41°C).
The temperatures recorded were as follows: day 20 (36.59°C), day 21 (36.51°C), day 22 (36.81°C), day 23 (36.50°C), day 24 (36.68°C), day 25 (36.78°C), day 26 (36.72°C), day 27 (36.82°C), day 28 (36.79°C), day 29 (36.63°C), day 30 (36.47°C), day 31 (36.47°C), and day 32 (36.28°C).
The next morning, on August 14, menstruation started, making this cycle 32 days long.
During the day 19 follow-up, the doctor mentioned that ovulation may have already occurred, or the follicle may have atrophied without ovulation.

Questions:
1.
Why would a nearly mature follicle atrophy?
2.
Is it possible for a follicle to shrink by 1 cm in just 2 days?
3.
Traditional Chinese medicine suggests that a temperature reading indicates ovulation; can a follicle measuring 1.7 cm still ovulate?
4.
Can body temperature still rise without ovulation?
*Typically, I take one vitamin in the morning, consume red bean soup and cherries during my menstrual cycle, and after menstruation, I take one vitamin in the morning, two capsules of Vitex, two capsules of inositol, drink black soybean milk, and take two capsules of Vitex and one capsule of inositol in the evening, along with herbal medicine.
I usually eat fruits like cherries, grapes, and apples.*

Xiao Yue Er, 30~39 year old female. Ask Date: 2019/08/15

Dr. Huang Jianzhong reply Obstetrics and Gynecology

These are very specialized and in-depth questions that should be discussed in detail with your attending physician.

Reply Date: 2019/08/15

More Info

Understanding ovulation and the fluctuations in body temperature during the menstrual cycle is crucial for women who are tracking their fertility or experiencing irregular cycles. The menstrual cycle is typically divided into several phases: the follicular phase, ovulation, and the luteal phase. Each phase is characterized by hormonal changes that influence ovulation and body temperature.

1. Follicular Phase: This phase begins on the first day of menstruation and lasts until ovulation. During this time, estrogen levels rise, leading to the maturation of follicles in the ovaries. The body temperature during this phase is generally lower, averaging around 36.1 to 36.5 degrees Celsius.

2. Ovulation: Ovulation occurs when a mature egg is released from the ovary, usually around the midpoint of the cycle. This is often accompanied by a slight drop in basal body temperature (BBT) followed by a rise of about 0.5 to 1 degree Celsius due to increased progesterone levels. The temperature rise indicates that ovulation has occurred. In your case, the weak positive ovulation test and the subsequent temperature fluctuations suggest that ovulation may have occurred, but the size of the follicle and its subsequent decline raises questions.

3. Luteal Phase: After ovulation, the luteal phase begins, characterized by elevated progesterone levels, which help prepare the uterine lining for potential implantation. The body temperature remains elevated during this phase, typically ranging from 36.5 to 37 degrees Celsius. If pregnancy does not occur, progesterone levels drop, leading to a decrease in temperature and the onset of menstruation.

Now, addressing your specific questions:
1. Why does a nearly mature follicle shrink?: Follicles can regress for several reasons, including hormonal imbalances, stress, or inadequate luteal support. If the hormonal signals are not optimal, the follicle may not reach full maturity or may degenerate instead of releasing an egg.

2. Can a follicle shrink by 1 cm in two days?: While it is uncommon for a follicle to shrink that rapidly, it is possible. Follicular dynamics can vary significantly among individuals, and factors such as hormonal levels and ovarian response can influence follicle size.

3. Will a 1.7 cm follicle ovulate?: Generally, a follicle needs to be around 1.8 cm or larger to be considered mature enough to ovulate. However, individual variations exist, and some follicles may still release an egg even if they are slightly smaller.

4. Can body temperature rise without ovulation?: Yes, it is possible for body temperature to rise without ovulation due to other factors such as hormonal fluctuations, illness, or stress. However, a sustained temperature increase over several days is often a strong indicator of ovulation.

In terms of your health regimen, it is commendable that you are taking vitamins and incorporating a balanced diet. However, if you are experiencing irregular cycles or difficulties with ovulation, it may be beneficial to consult with a healthcare provider or a fertility specialist. They can provide tailored advice and possibly recommend further testing to assess your hormonal levels and overall reproductive health.

In conclusion, understanding your menstrual cycle and the associated temperature changes can provide valuable insights into your reproductive health. If you have concerns about your cycles or ovulation, seeking professional medical advice is always a prudent step.

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