A simplified method for recording basal body temperature

JOURNAL OF ADOLESCENT HEALTH CARE 3:25-28, 1982

A Simplified Method for Recording Basal Body Temperature* IRIS F. LITT, M.D.

The present study was undertaken to evaluate thermocrystalography as a means of simplifying the recording of basal body temperature (BBT) for the purpose of determining the time of ovulation. Accordingly, BBT, as recorded by disposable oral thermocrystal thermometers manufactured for fever detection, was compared with that obtained by a conventional rectal glass thermometer to establish reliability of the method within the normal temperature range. The readings by both methods were comparable, with a nonsignificant difference between 109 readings when analyzed by a paired t test. A biphasic curve was easily discernable in each of the eight cycles monitored. The use of disposable thermocrystal thermometers provides an alternative to the conventional method of BBT determination, which is faster, easier to read, and potentially more acceptable because of its oral use.

KEY WORDS:

Ovulation Basal body temperature Fertility More than 100 years have elapsed since the fluctuations in body temperature and the menstrual cycle were described by Mary Putnam Jacobi (1). Since that time, advances in technology and the growing interest in problems of infertility and over population have established the relationship between ovulation and the biphasic basal body temperature curve (2).

*Supported in part by the Robert Wood Johnson Foundation. From the Department of Pediatrics, Stanford University School of Medicine, Stanford, California 94305. Please address reprint requests to Dr. Litt. Manuscript accepted 26 February 1982.

The standard procedure for recording basal body temperature (BBT) is to take a rectal temperature with a glass thermometer for a minimum of five minutes immediately upon awakening and before rising in the morning. There is normally a biphasic curve between two menstrual periods with a lower temperature level during the postmenstrual phase as compared to that during the premenstrual phase. Topographic differences have been noted with a shorter postmenstrual and longer premenstrual phase if the oral temperature is recorded. Recent developments in the field of thermocrystalography provide the technology for simplifying the task of recording body temperature. This technique had had clinical application for screening (3) and recording fevers (4). Its reliability in the normal range of body temperature has not yet been evaluated, nor has it been investigated as a method of detection of ovulation. The present study investigates thermocrystalography as a way of simplifying the process of obtaining a BBT.

Methods A rectal thermometer and one from the lot of disposable thermocrystal thermometers (DTTs) were calibrated, using a constant temperature water bath. In the initial phase of the study, four subjects obtained their BBT using a conventional glass rectal thermometer and a DTT, used orally, for a total of 109 days. For the second phase, two subjects, a nurse and a physician not using oral contraceptives, recorded their daily BBT over eight menstrual cycles. Body temperature was recorded between 6:30 and 7;00 A.M. under basal conditions (i.e., before rising from bed) with a standard rectal thermometer for 5

© Society for Adolescent Medicine, 1982 Published by Elsevier Science Publishing Co., Inc., 52 Vanderbilt Ave., New York, NY 10017

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0197-0070/82/010025 + 04502.75

Figure 1.

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Basal body temperature determinations by both methods in three cycles.

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SIMPLIFIED METHOD FOR BASAL BODY TEMPERATURE

Table 1. C o m p a r i s o n of Basal B o d y T e m p e r a t u r e D e t e r m i n a t i o n s by T w o M e t h o d s a Glass mercury thermometer (°C) Subject Subject Subject Subject

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37.2 36.6 37.2 36.8

:~- 0.2 :-~ 0.1 :-~ 0.1 :~- 0.1

Disposable thermometer (°C) 37.2 36.6 37.3 36.8

-+ 0.2 -+ 0.i + 0.1 --- 0.1

tained their final readings during that period. As the environmental temperature rose above that recorded by the DTTs, the increase in ambient temperature was detected and registered, thus erasing the temperature originally recorded. When placed in an insulated Container, the original recording was preserved for one month.

Discussion

aPaired t test--NS

min, and a DTT for I min. The DTT used is pictured in Fig. 1. The DTTs were stored in a home refrigerator prior to use. Temperature was recorded daily by both methods, and time of menstruation, abdominal pain, and mucorrhea noted. DTTs were labeled and retained at room temperature to determine the duration and stability of the color change over time.

Results There was concordance between the values obtained in the standard water bath by the standard rectal thermometer (36°C) and the DTT (35.9°C). There was no significant difference between the 109 initial phase paired readings (Table 1). BBT determinations showed a nearly identical biphasic pattern by both instruments, (Fig. 2, Table 2): The pre- and postmenstrual phases by both methods were also recorded according to the method of Vollman (5). During the first 16 days of the study, the room temperature remained below 36°C, and th e temperature recorded by the earliest preserved DTTs re-

This study suggests that an orai basal body temperature using a DTT may provide a fast, easily readable, and simple alternative to the standard rectal glass thermometer method. It may have the potential of minimizing compliance problems and allow BBT studies of adolescents, who are in general less well motivated than infertile couples/It eliminates the difficulty of reading a mercury thermometer, which may be a problem for some. The problem of breakage is obviously eliminated. Having a simple method for BBT determinations available will allow the monitoring of ovulation in teenagers with suspected endocrine problems, or as an educational aide, especially for those who are sexually active and concerned about the possibility of sterility.

The author wishes to thank Bio-Medical Sciences, Inc. for supplying the Uni-temp (single use thermometer); Emmet Lamb, M.D., for his critical review of the manuscript, and Rudolph Vollman, M.D., for his assistance with analysis of the data. Special thanks to Patrick Alvin, M.D., Shirley Rudd, R.N., and Robin Henson for agreeing to provide data for this study, and to Elizabeth Brown for her assistance in processing the data. "

Table 2. Basal B o d y T e m p e r a t u r e D e t e r m i n a t i o n s for Six M e n s t r u a l Cycles in Subject i

Measurement method Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6

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Rectal (glass) Oral (dis ~osable) Rectal (glass) Oral (dis ~osable) Rectal (glass) Oral (dis ~osable) Rectal (glass) Oral (dis ~osable) Rectal (glass) Oral (dis ~osable) Rectal (glass) Oral (dis ~osable)

aPaired t Test--NS

Mean temperatur e for each cyclea 37.07 37.14 37.11 37.07 37.04 37.09 37.24 37.19 37.02 36.95 37.16 37.14

_ 0.17°C __+ 0.15°C _+ 0.22°C _+ 0.23°C _+ 0.18°C ___ 0.18°C _ 0.19°C -+ 0.18°C _+ 0.14°C -+ 0.12°C - 0.24°C _+ 0.21°C

Length of phases (days) Postmenstrual

Premenstrual

16 17 12 12 16 16 12 12 18 18 17 16

12 1I 14 14 11 11 14 14 13 13 10 11

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LITT

References 1. JacobiMP: The Question of Rest for Women During Menstruation, New York: Putnam's Sons, 1877 2. Zuck TT: The relation of basal body temperature to fertility and sterility in women. Am J Obstet Gyneco136:998-1005, 1938 3. Lees DE, Schuette W, Bull JM, et al.: An evaluation of liquid-

JOURNAL OF ADOLESCENT HEALTH CARE Vol. 3, No. 1

crysta! thermometry as a screening device for intraoperative hyperthermia. Anesth Analg 57:669-674, 1978 4. McAliister TA: A single-use clinical thermometer. Scott Med J 20:300-304, 1975 5. Vollman R: The Menstrual Cycle in Major Problems in Obstetrics and Gynecology. Vol. 7, Philadelphia: W. B. Saunders, 1977