The basal body temperature measurement can help you know when you are ovulating, so it can guide you when to have intercourse, when to use safe contraception, and patients with delayed menstruation can know when their period will come by taking the temperature measurement. The first thing we will talk about is the basal body temperature measurement method. The basal body temperature of normal women of childbearing age varies cyclically, as does the menstrual cycle. This temperature change is related to ovulation. Under normal circumstances, a woman’s basal body temperature is low before ovulation and increases after ovulation. This is because the corpus luteum formed after ovulation and the secretion of more progesterone stimulates the hypothalamic thermoregulatory center, causing the basal body temperature to rise and continue to fall until the next menstrual period. After ovulation, progesterone secretion increases, which can raise the basal body temperature. Therefore, when the body temperature rises from low to high (by 0.3 degrees Celsius or more), it means that ovulation has been completed. What should be noted during the measurement process: Every morning after waking up, do not talk, do not move, do not get up, and immediately measure the oral (or anal or axillary) body temperature for more than 3 minutes. Record daily on the temperature recording sheet for easy observation. The day of ovulation and the three consecutive days thereafter are the fertile period. It is best to use a thermometer specifically designed for basal body temperature measurement, as this will make the results more accurate. In case of cold, fever, diarrhea, insomnia, alcohol consumption, use of electric blankets, etc., the basal body temperature is often easily affected and should be explained at the bottom of the table. In order to improve the correctness of measuring basal body temperature, the mercury column on the thermometer should be dumped below 35 degrees Celsius every night before going to bed, and it should be placed on the bedside table or by the pillow so that it can be taken at hand when it is used, minimizing activities. If you get up to take the thermometer, it will raise the basal body temperature and make the temperature values for the day meaningless. For women who work mid-shift or night shift, place the basal body temperature measurement at the time of first awakening 4 to 6 hours after each bedtime. Basal body temperature usually needs to be measured for more than 3 consecutive menstrual cycles. By recording the basal body temperature measured every day on a temperature record sheet and connecting it to a curve, you can see that the body temperature is low in the first half of menstruation and rises in the second half of menstruation. This is called a biphasic temperature curve. It is thought that the lowest point before the rise in temperature is the day of ovulation, but this is not the case in most women, and only about 20% of women show this. After observing your chart, find the “fertile period” – within 3 days of the rise in basal body temperature, from day 4 until the next menstrual period, which is the “post-ovulatory period”. Generally speaking, basal body temperature is used more for women who want to get pregnant than for women who want to use contraception. Because basal body temperature only indicates that ovulation has occurred, I can determine the safe period after ovulation. However, this method does not “predict” when ovulation will occur, so it cannot determine the safe period before ovulation, in other words, there is still a chance of conception if you have intercourse before you determine when you will ovulate in the month. In most cases, basal body temperature measurement is very reliable for determining the safe period after ovulation, but sometimes there are irregularities in the temperature curve that make it impossible to determine the exact time of ovulation, and in this case, it is not possible to use the safe period for contraception. This is because some women’s hormonal balance does not clearly show high and low temperature fluctuations. If the hormonal balance is not good, having sex even during menstruation may result in pregnancy. It is mentioned that the risk period starts on the 5th day of menstruation, but it is limited to mature women. Warning on the use of the “basal body temperature measurement method” 1. This method does not “predict” when ovulation will occur, so the safe period before ovulation cannot be determined, and there is still a chance of conception if you have intercourse before determining when you will ovulate this month. 2. This method is more suitable for women who are not affected by their physical condition and can clearly show high and low temperature periods.