Basal body temperature is the temperature of the body at rest, i.e. the temperature measured after 6-8 hours of sleep and rest, before getting up, eating or talking. Basal body temperature can indirectly reflect ovarian function in women. The basal body temperature of a normal woman during her fertile period is slightly lower after her period, and may be lower on the day of ovulation, but after ovulation, due to the formation of the corpus luteum in the ovaries, the basal body temperature rises until the next period when it falls again.
I. Measurement method
1, equipped with a temperature table, master the table reading method, to ensure accurate.
2, the temperature table placed on the side of the bed table, every night before going to bed to swing the mercury column low.
3, every morning after waking up, immediately measure the sublingual body temperature in the mouth for 5 minutes. If you can take the temperature at a fixed time every morning (5:00~7:00), it is better. It is strictly prohibited to get up, urinate and defecate, smoke, eat, talk, etc. before taking the temperature, and record the temperature in this table after measurement. Night shift workers should sleep and rest 6-8 hours after the above method of temperature measurement.
4.If there is sexual life, it should be indicated in the table.
5, cold, alcohol, late sleep, insomnia and other circumstances, often affect the body temperature. Should be written in each note, for reference.
6.If there is any transient lower abdominal pain, vaginal bleeding, leucorrhoea, increased sensuality or other abnormalities during the cycle. These should be noted in the notes.
7.The start and stop dates of examination, treatment and medication should be indicated in the remarks.
8. Use a form for each menstrual cycle, and start recording from the left side of the form, and start with x table of menstrual periods.
Basal body temperature
Biphasic temperature curve: The normal basal body temperature is biphasic, i.e. the follicular phase is the low temperature phase and the luteal phase is the high temperature phase. The low temperature phase lasts for about 2 weeks, and the high temperature phase lasts for 12~16 days, with an average of about 14 days. From the day of ovulation to the next menstrual day, the body temperature rises by 0.3~0.5℃. Before the temperature rise, there is usually a low point of temperature (some people may have none), and then the temperature rises sharply. This kind of temperature curve which is low before and high after (low before ovulation and high after ovulation) is called biphasic temperature curve and suggests ovulation of the ovaries.
Monophasic basal body temperature: The high and low temperature phases cannot be clearly distinguished during the menstrual cycle, which is called monophasic basal body temperature. It indicates poor ovarian function and no ovulation.
Clinical significance
1.Estimation of ovulation period
Basal body temperature is difficult to accurately determine the ovulation date, but it can roughly estimate the ovulation period, and the accuracy of predicting ovulation is about 84%. Ovulation usually occurs 1~2 days before the rise of body temperature or during the rise from the low temperature phase to the high temperature phase.
Some people have a 0.3~0.5℃ drop in basal body temperature during ovulation, which is due to the high level of estrogen prompting an increase in acetylcholine, causing vasodilation and increasing heat dissipation; some people do not have a drop in body temperature. Some scholars found that 5% of ovulation occurs 1 day before the day of lowest body temperature, 22% on the day of lowest body temperature, 40% at the end of low body temperature, and 25% on the first day of high body temperature.
2.Guiding conception Sexual intercourse on or within 24 hours before or after the estimated day of ovulation can easily lead to conception.
3.Understanding luteal function Basal body temperature should rise immediately after ovulation, with high temperature maintained for 12~16 days, average 14 days, with normal luteal function, high temperature phase up to 12 days.
① Luteal insufficiency.
Clinical manifestations are shortened menstrual cycle, or menstrual cycle is within the normal range, but the patient is not easy to conceive or miscarriage in early pregnancy. The basal body temperature is biphasic, but the high temperature phase is too short, less than 12 days, especially less than 11 days; or low temperature to high temperature in a “step” slowly rising (more than 3 days); or the rise is low, the rise is less than 0.3 ℃; or the basal body temperature is unstable (high temperature phase fluctuations of more than 0.1 ℃); or a small amount of high temperature end Vaginal bleeding, all suggest luteal insufficiency.
Luteal atrophy: prolonged menstrual period. Basal body temperature shows a slow decline in the high temperature phase. The menstrual period is still high-temperature phase body temperature.
4. Diagnosis of luteinization syndrome (LUFS) with ultrasound
Follicular luteinization syndrome refers to the development of follicles without ovulation, but the granulosa cells are luteinized to secrete progesterone, and the basal body temperature is biphasic. The diagnosis of non-ruptured follicular luteinization syndrome can be made by ultrasound detection of follicles that are not smaller or larger during the hyperthermia period.
5.Diagnosis of early pregnancy
Basal body temperature continues to rise for 16~18 days (without HCG) suggesting possible early pregnancy; over 20 days, early pregnancy can be confirmed. Gradual decrease in basal body temperature during early pregnancy suggests luteal insufficiency and a tendency to miscarriage.
6.Indirect understanding of ovarian function Generally, biphasic body temperature with ovulation, monophasic body temperature without ovulation, indirectly reflecting ovarian (reserve) function.
7.Other
Basal body temperature does not decrease during menstruation, except for luteal atrophy, it may also be caused by absorption heat after bleeding from ectopic lesions of endometriosis. Primary amenorrhea with biphasic type of basal body temperature should be considered uterine type amenorrhea, such as absence of uterus or tuberculosis destroying endometrium.