Using Circadian Rhythm Patterns of Continuous Core Body Temperature to Improve Fertility and Pregnancy Planning

Abstract

Objective: Review relationships among circadian clocks, core body temperature (CBT), and fertility in women.

Methods: Scoping literature review.

Results: Circadian clocks are a ubiquitous adaptation to the most predictable environmental events - the daily cycles of light and dark. Core body temperature (CBT) also follows a circadian rhythm. Additionally, CBT is tightly controlled by a combination of neuronal circuits that begin in the hypothalamus and involve many other portions of the brain as well as a wide range of peripheral mechanisms. In women with normal reproductive function, the diurnal temperature pattern for CBT is strongly influenced by the menstrual cycle of reproductive hormones, primarily estradiol and progesterone, which modulate the activity of hypothalamic neural circuits involved in body temperature control, resulting in an infradian CBT rhythm.

Conclusions: Analysis of CBT via continuous recording reveals patterns in the interactions of circadian and infradian CBT rhythms capable of accurately predicting the fertility window and hormonal patterns suggesting oligo-ovulation and subfertility. New wearable technologies can facilitate employment of hormone-associated changes in CBT for pregnancy planning and offer clinical insight to infertility and menopause.

Keywords: circadian; core temperature; estrogen; fertility; hypothalamus; infradian; menstrual rhythm; progesterone.

Figure 1

Continuous core body temperature (CCBT) collected during the menstrual cycle reveal an infradian rhythm and pattern. The fine purple line represents a cosinor fit of continuous core body temperature influenced by the combined effect of estrogen and progesterone. Arrows indicate the predominate influence of estrogen in the peri-ovulatory period of the follicular phase and the predominate influence of progesterone in the luteal phase. Analysis of the change in phase, amplitude and mesor of CCBT predict and identify the window of fertility and day of ovulation and mensus.