Delayed menstruation If the basal body temperature is measured during the menstrual cycle, the temperature rises and does not fall when menstruation is delayed. This indicates a very high probability of pregnancy. Chorionic gonadotropin can be measured in the blood at this point, and if it rises it indicates pregnancy. Normally, the temperature drops on the 14th day after ovulation, and then vaginal bleeding occurs, indicating menstruation. If the temperature continues for more than 17 days without dropping, you can be almost certain that you are pregnant. Therefore, if the basal body temperature drops, you will usually have your period by the next day. However, a very high body temperature beyond 37 degrees may be due to fever from a cold or other infectious diseases. It is important to go to the hospital in time for examination.