The basal temperature drops in the luteal phase

Why does temperature drop in the luteal phase / post-ovulatory phase, which we refer to colloquially as PO?

It often happens that when compiling basal temperature graphs, drops occur in the OP. What can they be caused by?

There are various reasons, let’s see them one by one:

• measurement time : the measurement on the day of the drop was recorded more than an hour and a half earlier than usual. We know that the basal temperature, taken in absolute rest, depends on the time in which the measurement is made. If I measure the tb late at night I will detect lower temperatures than those detected for example at 9 in the morning and this with the same hours of continuous sleep behind me. See: how the basal body temperature varies based on the time of measurement
• During the luteal phase there is a second small rise in estrogen   which can cause a temporary drop in temperature. This decline often coincides with a day or two of runny cervical mucus. This doesn’t mean you are fertile again for that cycle, ovulation has already occurred!
• the decline from implantation : it is not always possible to notice in the pregnancy graphs and for it to be defined as such there must be a positive pregnancy test. The test is carried out about one week after implantation loss (and therefore two weeks after ovulation)
• altered measurement : it can happen that you measure your tb with less than 3-4 hours of continuous sleep behind you, it can happen that you ate late the night before, slept badly at night, slept with the window open or with the air conditioning running through the stars and having been cold… All of this can affect the correctness of the basal temperature, altering it.

The basal temperature drops around menstruation

How does the basal temperature decrease in conjunction with menstruation?

In case of non-conception it could start to decrease progressively between 10 and 12 hours. On the other hand, there is a very significant drop on the day of menstruation (sometimes already the day before).

Attention: the temperature during menstruation may undergo a slight increase which may be due to the residual progesterone in the circulation or to the hormonal fluctuations that occur during menstruation.

Towards the end of menstruation, the temperature should drop to the values ​​typical of one’s follicular phase.