Types of Basal Temperature Charts

Types of basal temperature charts

In the domestic classic manuals on gynecology of past years, five main types of temperature curves are described:

Type I – temperature increase in the second phase of the cycle by at least 0.4 C; there is a preovulatory and premenstrual drop in temperature. The duration of the temperature increase is 12-14 days. This curve is typical for a normal two-phase menstrual cycle;

Type II – there is a mild rise in temperature (0.2-0.3 C) in the second phase. This curve indicates estrogen-progesterone deficiency;

Type III – the temperature rises shortly before menstruation and there is no premenstrual drop. The second phase is shorter than 10 days. This curve is typical for a two-phase menstrual cycle with insufficiency of the second phase;

IY type – monotonic curve (no changes throughout the entire cycle). This curve is observed during an anovulatory (no ovulation) cycle;

Y type – atypical (chaotic) temperature curve. There are large temperature ranges that do not fit into any of the types described above. This type of curve can be observed with severe estrogen deficiency, and may also depend on random factors.

An increase in basal temperature occurs when serum progesterone levels exceed 2.5-4.0 ng/ml (7.6-12.7 nmol/l). However, monophasic basal temperature has been identified in a number of patients with normal progesterone levels in the second phase of the cycle. In addition, monophasic basal temperature is observed in approximately 20% of ovulatory cycles. A simple statement of biphasic basal temperature does not prove the normal function of the corpus luteum. Basal temperature also cannot be used to determine the time of ovulation, since even during luteinization of an unovulated follicle, a two-phase basal temperature is observed. Nevertheless, the duration of the luteal phase in accordance with basal temperature data and the low rate of rise in basal temperature after ovulation are accepted by many authors as criteria for diagnosing luteinization syndrome of a non-ovulating follicle.