CHANGES IN BASAL BODY TEMPERATURES AND THE PREDICTION OF THE ONSET OF LABOR by Caron Candace Campbell A thesis submitted to the faculty of The University of Utah in partial fulfillment of the requirements for the degree of Master of Science College of Nursing The University of Utah August 1982 G)1982 Caron Candace Campbell All Rights Reserved THE UNIVERSITY OF UTAH CRADUATE SCI-IOOL SUPERVISORY COMMITTEE APPROVAL of a thesis submitted by Caron Candace Campbell This thesis has been read by each member of the following su pervisory committee and by m�jorit y vote has been fou nd to be satisfactory. THE UNIVERSITY OF UTAH GRADUATE SCHOOL FINAL READING APPROVAL To the Graduate Council of The University of Utah: I have read the thesis of Caron Candace Campbell In Its final form and have found that (I) its format, citations, and bibliographic style are consistent and acceptable; (2) its illustrative materials including figures, tables, and charts are in place; and (3) the final manuscript is satisfactory to the Supervisory Committee and is ready for submission to the Graduate School. Date Lorraine Sevcovic, M.S., Member. Supervisory Committee Approved for the Major Department Linda K. Amos, Ed.D., F.A.A.N. Chairman! Dean Approved for the Graduate Council James L. Clay to Dean or The Graduate Schoo1 C.N.M. ABSTRACT Pregnant women were requested to chart daily basal body temperatures from the 37th week of gestation until the birth of their infants in order to examine whether changes in basal body temperatures occur in relationship to the spontaneous onset of labor in such a way the labor can thus be predicted. Thirty-five women entered the study, resulting in 3 vaginal temperature and 16 oral temperature charts which met criteria for spontaneous labor. Mean vaginal and oral temperatures did not differ significantly. Charts meeting criteria for spontaneous onset of labor were analyzed for significant changes in basal body temperatures with the cumulative sum (CUSUM) test. Nine charts (47.4%) had erratic patterns with no significant changes in baseline basal body temperatures. Five charts (26.3%) demonstrated a significant drop in temperature 2-6 days (mean=3.4 days) before the onset of labor. Four charts (21.1%) had a significant drop 16-19 days (mean=17.5 days) prior to labor. One chart (5.2%) signalled a drop 30 days before labor. Changes in basal body temperatures observed in these subjects have too much individual variation to support the use of temperature charting and analysis as a tool which can predict the spontaneous onset of labor. v CONTENTS ABSTRACT. . . . ACKNOWLEDGMENTS . iv . viii Chapter I. II. INTRODUCTION • • 1 Purpose . . . . • • Conceptual Framework • • Review of Literature • • • • • Swine • . . • • Dogs . • • • • Sheep. . •• Goats. Cattle . . • • . . • • . Primates . Women. • • Research Questions • . . • • • 2 3 5 6 6 7 7 8 8 8 8 METHODOLOGY. 10 Subjects . . • • • • • • . Definitions • . . • • • ••• • • • Basal Body Temperature • • • • Term Pregnancy • • • • . Onset of Spontaneous Labor • . Data Collection Procedures • • • • • Assumptions . . . • • . 10 10 10 10 DATA ANALYSIS • . 14 IV. RESULTS . • 17 V. DISCUSSION. 27 Research Question One . Research Question Two • . . • . Progesterone and Thermoregulation in Pregnancy. . • • . •.• . . . • • • . 27 27 III. 11 11 13 28 VI. SUMI~RY . 31 Appendices A. INSTRUCTIONS TO PARTICIPANTS. B. BASAL BODY TEMPERATURE CHART. REFERENCES • . . . . . • . • • • . vii . 33 . . . • . . 36 • • • . 39 ACKNOWLEDGMENTS This thesis was a delightful experience thanks to the support and teaching of special individuals. I wish to credit Mary Anne Graf, M.S., C.N.M., for the original idea for this study, which arose out of discussions about her very fertile Samoyed, Delight. I am partic- ularly grateful to Richard Worley, M.D., who guided me through the fascinating intricacies of reproductive endocrinology. Dr. Worley also offered encouragement and constructive suggestions throughout this process which enhanced my learning and improved the quality of this work immeasurably. I wish to express appreciation of Marlene Egger, PhD., who patiently helped me interpret the CUSUM test and generously shared her time and equipment for the data analysis. Lorraine Sevcovic, M.S., C.N.M. has my gratitude for doing all those things a chairperson must do while maintaining enthusiatic support. Special thanks to Sid Spencer of Bergen-Brunswig Drug Company for supplying basal body temperature thermometers for the study. CHAPTER I INTRODUCTION AND REVIEW OF LITERATURE Many attempts have been made to predict precisely when labor and birth will occur. A due date or estimated date of confinement (EDC) is computed using the mean duration of normal pregnancy, known to be 280 days past the last normal menstrual period (LNMP). The range, however, is between two weeks before and two weeks after the EDC. Signs and symptoms of impending labor often observed in women are lightening, cervical changes, false labor, premature rupture of membranes, bloody show, an energy spurt, and gastrointestinal upsets (Varney, 1980). Un- fortunately, these signs and symptoms may appear any time from hours to weeks before true labor begins. In mammals, similar changes are observed before parturition: relaxation of pelvic ligaments, mucoid dis- charge, vulvar swelling, restlessness, soft or' more fre-' quent stools, and a change in body temperature. In some species, the change in body temperature is predictive 2 within hours of the onset of parturition. Whether or not changes in basal body temperature (BBT) in women occur prior to the onset of labor is unknown. If there is a detectable shift in BBT which is consistent in its relationship to the onset of labor, it may prove a valuable tool to aid management of care and preparation for labor and birth. For example, pregnant women and their families could initiate contingency plans for child care, household maintenance, and wor k absences. Adequa te rest and nutrition could be encouraged, and anxieties stemming from uncertainties about labor onset may be eased, so that labor is entered in a well-rested, relaxed state. Care providers could assure completeness of antenatal care and education, and revise plans as necessary. They could inform hospitals or birth centers of the client's status and confirm that antenatal records were up-to-date and available. Knowledge that labor is imminent could allow the freedom to await spontaneous labor rather than inducing labor in some cases. Thus, the ability to predict the onset of labor may have broad economic, sociological, psychological, and medical ramifications • . P'u:rpo'Se The purpose of this study was to examine the rela- 3 tionship between basal body temperature and the spontaneous onset of labor in women at term. Conceptual Framewo'r k Body temperature is a balance between heat loss and heat production, which in mammals is regulated in the central nervous system by the hypothalamus. The hypothalamus operates as a thermostat which is influenced by a complex interaction of chemical, environmental, and hormonal inputs. One hormone known to affect BBT, apparently by a direct effect on the hypothalamus, is progesterone. The thermogenic effects of progesterone are responsible for the rise in BBT observed in the luteal phase of ovulatory menstrual cycles in women. As the plasma progesterone concentration increases following ovulation, so also does the BBT. Conversely, when progesterone concentration falls at the end of a cycle, the BBT returns to the preovulatory baseline. If conception and implantation occur during a cycle, the elevated plasma progesterone concentration is maintained by the corpus luteum, and the BBT remains at or above the postovulatory level. Later in pregnancy, the placenta becomes the site of progesterone production, and plasma concentration continues to rise gradually until 4 delivery (Pritchard & MacDonald, 1980). In many animal species, the plasma progesterone concentration is known to fall prior to the onset of labor and is believed to play an important role in the initiation of labor (Tulchinsky & Ryan, 1980). Not surprisingly, a decline in body temperature has been observed following a drop in progesterone concentration. For example, in the bitch progesterone falls sharply 36-48 hours prepartum, followed by a decline in body temperature 24 hours before parturition (Concannon, Powers, Holder & Hansel, 1977). Similar declines in plasma progesterone and body temperature associated with imminent parturition have been documented in cows and ewes (Ewbank, 1969; Winfield, Makin Concannon et & Williams, 1973; Dufty, 1971; al., 1977). Declines in progesterone and body temperatures are not a universal finding in mammals, however. In nonhuman primates and women plasma progesterone concentrations do not routinely fall prior to the onset of labor (Walsh & Novy, 1981; Boroditsky, Reyes, Winter & Faiman, 1978; Tulchinsky & Ryan, 1980), although there is speculation that alteration of the metabolism of the hormone in the maternal or fetal compartment may be occurring. sky and Ryan suggested that Tulchin- a fall in hormone levels in the uterus may not be reflected in plasma concentra- 5 tion, or that there are other cellular determinants involved, such as receptor availability. By the same logic, it is also conceivable that there may be changes in receptor availability in the hypothalamus which account for declines in body temperature before labor, even when the plasma progesterone concentration remains elevated. Thus, it is appropriate to wonder if women may exhibit changes in BBT associated wi th immine.nt labor in spi te of unchang ing plasma progesterone concentrations. Revi'e'w' of' 'Li'te'r'atu'r e Observations of preparturient body temperature changes have appeared in veterinary literature for many decades. Weisz (1943) reviewed Austrian and German veterinary journals and concluded that cows, mares, does, goats, sows, and dogs had distinct decreases in body temperatures within a day or two of parturition; sheep and cats had declines that were too indistinct for practical purposes. Research during the last dozen years has provided scientific documentation of changes in body temperature and its relationship to parturition in the following species: 6 Swine Hendrix, Kelley, Gaskins, and Bendel (1978) found o an increase of O.4 Cin rectal temperatures beginning 4 hours before parturition. Littledike, Witzel, and Riley 0 (1979) observed an increase of 1. 4 C beg inning approximately 12 hours before the birth of the first pig. Similarly, Elmore, Martin, Riley, and Littledike (1979) 0 noted an increase of 0.6-1. 2 C in farrowing swine 13 +4.1 hours before parturition. Conversely, King, Willoughby, and Hacker (1972) observed a subnormal temperature for at least one week prior to farrowing, ascribing the increase in rectal temperatures coincidental with labor to the sows' creased activity levels. in- They concluded that rectal temperatures could not be used to predict farrowing. Research on dogs has produced similarly varying results. Kirk, McEnter, and Bentinck-Smith (1968) des- cribed a "decided drop in rectal temperature" at the onset of labor, but did not quantify the decrease other than to note that it may be as low as 98 o F. Griesemer and Gibson (1963) used the observed drop in rectal temperature as well as other signs to time the operative deliveries of gnotobiotic (germ-free) dogs. Concannon, Powers, Holder, and Hansel (1977) dis- 7 covered a distinct transient hypothermia in 78/80 bitches which occurred 8-24 hours prior to parturition. However, Long, Mezza, and Krakowka (1978) concluded that a drop in rectal temperature was of some value, but too variable among individuals to be used as the sole criterion for predicting impending labor. Sheep Ewbank (1969) found a consistent drop in temperatures of sheep in the 54 hours preceding lambing, but individual variation prevented accurate pinpointing of the exact time of parturition. Winfield, Makin, and Williams (1973) measured temperatures at different times of day and discovered that early morning temperatures showing a fall of O.3 0 C or greater from previous consecutive monning readings indicated that parturition was imminent. Their research also confirmed Ewbank's findings. Goats Jones and Knifton (1971) failed to demonstrate any obvious or uniform temperature changes in goats which could be used to predict the first stage of labor. Cattle Dufty (1971) observed a fall in rectal temperatures immediately prior to parturition, but commented that 8 they were highly variable and frequently confused with normal daily fluctuations, and thus were not useful as a diagnostic tool. Pr imates Ruppenthal and Goodlin (1981) noted dramatic declines in temperatures measured by subcutaneous temperature transmitters in pig-tailed macaques (M'aca'c'a' n'em'estrina) 1-2 hours prior to the expulsion of fetuses. Women Changes in basal body temperatures of women have been studied extensively during the menstrual cycle, but not during full-term pregnancy. Burd (1977) investigated mammary temperatures as measured by thermograms for 29 days preceding parturition, and found no significant changes until the first postpartum day. In a self-report, Yewlett (1979) outlined the results of temperatures taken 0 daily during her pregnancy which showed a O.3 C drop 4 days before spontaneous labor with her second child. Goodlin (1981) reviewed daily temperatures of hospitalized women at term, but found no significant changes before labor began. Research Questions 1. Is there a change in basal body temperature related 9 to the spontaneous onset of labor in women at term? 2. Can observation of basal body temperatures in women at term permit clinically useful predictions of the onset of spontaneous labor? CHAPTER II METHODOLOGY Subjects Thir:ty-five women participated in the research. Of these, 14 (40%) volunteered during prenatal visits in private obstetrical practices. The remaining 21 subjects (60%) were volunteers from late pregnancy childbirth education classes. Basal Body Tempe'ra'tu're Basal Body Temperature (BBT) is conceptually defined as the measurement of heat being produced by the body at complete rest as a result of basal metabolic activity. BBT is operationally defined as the oral or vaginal temperature taken before any activity after at least four hours of consecutive sleep. Term Pregnancy Term Pregnancy is defined both conceptually and operationally as a pregnancy that has advanced beyond 38, but not more than 42 weeks of gestation completed since the first day of the last normal menstrual period 11 (LNMP). For the purpose of this investigation, if the LNMP was unclear, the estimated date of confinement (EDC) determined by the care provider was considered 40 weeks of gestation completed. Onset of Spontaneous Labor Onset of spontaneous labor is defined conceptually as spontaneous uterine contractions of sufficient fre·"'t quency, intensity, and duration to bring about readily demonstrable effacement and dilatation of the cervix. The operational definition is the spontaneous occurrence of regular uterine contractions accompanying cervical changes validated by a care provider or health care personnel which result in birth of the child within 36 hour s. Da ta CoTlection P'roc'edu'r'es Subjects were instructed to take and record daily temperatures at the same time every day after at least 4 hours consecutive sleep whenever possible. They were asked to note interruptions of sleep, fever or illness, medications other than vitamins or iron, or anything unusual which they thought might have affected their temperatures. 12 In addition to daily temperatures, subjects recorded the following information about their labors and births: date and time of onset of regular contractions, date and time of rupture of membranes and whether rupture was spontaneous or artificial, time of admission to the hospital, time and date of the birth, type of delivery (vaginal/forceps/cesarean), and medications used during labor (including pitocin and epidural anesthesia). The subject's gravidity, parity, age, LNMP, and EDC were also recorded on the chart. Subjects were provided with written instructions (Appendix A), BBT charts (Appendix B), Becton-Dickinson Basal Temperature thermometers, and a stamped envelope addressed to the investigator for returning completed charts. Subjects were checked for ability to read the basal thermometer accurately. Each subject was given a date to begin recording temperatures which was either the day that 37 weeks of gestation had been completed since the LNMP, or 21 days before the EDC as determined by other means such as sonography or clinical estimates in those cases where the LNMP was unclear. This was to allow at least a week of baseline temperature recordings in women who truly delivered at term. Confidentiality was protected by coding charts with 13 the number of the individual's consent form. The con- sent forms recorded the subject's address and phone number. Interested subjects were promised a summary of the outcome of the study. Assumptions Accuracy of the thermometers and the subjects' recording of temperatures was assumed. The assumption was also made that the temperatures noted by sujects were accurate measrues of basal temperatures, whether taken orally or vaginally, if taken according to the instructions. CHAPTER III DATA ANALYSIS Charts were analyzed for significant changes in BBT's using the cumulative sum (CUSUM) test, which has been shown to be a reliable statistical method for detecting BBT shifts in ovulatory menstrual cycles (Royston & Abrams, 1980). Xl' x 2 · In the CUSUM test, sequential values • .x r '· • .x N of BBT's are examined to detect a shift in the mean BBT's beyond a baseline value of B. If the mean E(X) of subsequent BBTls is less than B, these negative deviations predominate and a significant change in BBT is signalled. where The change of interest in E(X) is = var (X). ~ 2 A hypothesis test is applied in which the null hypothesis H : E(X) o alternative HI: E(X) =B > -- B is tested against an S~. CUSUM's are calculated as cumulative deviations of the sample BBT values X r about B - ~ scr , which is a central reference value. The CUSUM test is performed as follows: the CUSUM derived from sample values x rule, r let s r be according to the 15 = 0, = min (0, Sr-l + Xr r HO is rejected if Sr < h = 0- , (b - ~ Ej v ). 1,2, . . . , N the decision interval, and a significant drop in E(X) is judged to have occurred. In this application of the CUSUM test, B is the mean of the first three temperature readings, or three other sequential readings which were more representative of the baseline if the first three readings were uncharacteristic of the majority of readings. (An alternative sequence is indicated by a bar above the graphs in Figures one through three). The critical value h was calculated to yield an overall significance level of ~ = 6 (j" .05. The magnitude of the change of interest was set at o. SOF. Since CUSUM's that are calculated indefinitely will eventually signal a shift, an estimated run length L is programmed into the test. For example in average men- strual cycles this value L is set at 12. L was set at 17 based on In this study, findings in the literature that suggested a change in temperature may occur within 4 days of labor. Since these subjects began recording temperatures at 37 weeks gestation, or 21 days before 16 their EDC's, L was calculated by subtracting 4 from 21. Temperatures that were apparently influenced by interruptions or alterations in sleep patterns, medications, illness, or other unusual events noted by the subjects were omitted from the CUSUM calculations. Significance of differences observed between groups was determined using the t-test. CHAPTER IV RESULTS From the 35 subjects 19 charts (54%) were received which met the criteria of uncomplicated pregnancy and spontaneous onset of labor. Of the remaining 16 subjects, 5 (14%) delivered before 37 weeks gestation, 1 (3%) was induced, 1 (3%) was on bedrest for 19 days prior to the onset of labor, 1 broke her thermometer but did not request another, 1 (3%) had a thermometer that "didn 1 t work" but did not request another. One (3%) stopped tak- ing her temperature after her due date passed, 1 (3%) was still undelivered at the time of data analysis, and 5 (14%) failed to respond to mail or phone inquiries (see Ta ble 1). Eleven subjects agreed to take vaginal temperatures; 3 (27%) charts were returned. Of the remaining 8 subjects, 3 delivered early, 1 had a broken thermometer, 1 stopped taking her temperatures, and 3 did not respond to in~ quiries (see Table 2). Twenty-four subjects agreed to take oral temperatures, from whom 16 charts (67%) could be used for analysis. Of the 8 remaining subjects, 1 was induced, 18 Table 1 Outcomes for Subjects Participating in the Study N % Subject Numbers 19 54% 6,8,9,11,13,15,16 17,20,21,22,23,25, 26,27,28,31,33,35 Induction 1 3% 18 Bedrest 1 3% 32 Thermometer failure 1 3% 24 Broken thermometer 1 3% 3 Delivered early 5 14% 4,19,12,2,30 No response 5 14% 1,5,7,29,34 Quit taking temps 1 3% 10 Undelivered 1 3% 14 35 100% Acceptable charts Total 19 Table 2 Outcomes for Subjects Taking Vaginal Temperatures Percentage 3/11 Acceptable charts 27% 8/11 Not available 73% 3 delivered early 3 no response 1 quit taking temps 1 broken thermometer 20 1 was undelivered, and 2 failed to respond to inquiries. (see table 3). From the 14 subjects recruited' from private prac+ tices, 6 charts (43%) met criteria for analysis. The remaining 8 were the same subjects lost from the vaginal temperature group. From the 21 subjects recruited in childbirth classes, 13 charts (61%) met criteria for analysis. The remaining 8 subjects were the same ones lost from the oral temperature group. The ages of all subjects ranged from 16-34, with the mean age being 24.78 years (SO=3.87). Of the 19 charts used for analysis, the subjects' ages ranged 1930, with a mean of 24.84 years (SO=3.2). The difference was not significant. Fifteen primiparous and 4 mUltiparous women returned charts that met the criteria for analysis. Oata is incomplete on the parity of the remaining subjects because that information was generally not recorded on the consent forms in addition to the charts. Temperatures on the charts ranged between 96.3 0 and 0 98.5 0 F, with an average mean temperature of 97.71 F (SO=0.195) . o The average standard deviation was 0.24 F. Vaginal temperatures were not significantly different than oral temperatures. 21 Table 3 Outcomes for Subjects Taking Oral Temperatures Percentage 16/24 Acceptable charts 67% 8/24 Not available 23% 2 delivered early 2 no response 1 undelivered 1 thermometer failure 1 induction 1 bedrest 22 Among the charts analyzed by the CUSUM test 9/19 (47.4%) had erratic patterns with no demonstrable changes in BBT (Figure 1). Five charts (26.3%) showed a significant change in BBT 2-6 days prior to the onset of labor. terval was 3.4 days (SD=1.95). The mean in- All the subjects were primiparous (Figure 2). Four charts (21.1%) signalled significant changes 16-19 in BBT days before labor, the mean being 17.5 days (SD=1.29) Of these four subjects, 2/4 (50%) were primiparous and 2/4 (50%) were multiparous. (Of interest is chart #32, which also showed a significant drop 19 days before spontaneous labor. However, the confounding influence of the subject's bedrest eliminated this chart from formal analysis) (Figure 3). One chart (5.2%) had a significant drop in temperature 30 days before spontaneous labor (Figure 4). In several cases (#11, 15, 23, 26, and 31) the BBT rose again after the significant drop signalled by the CUSUM test, either in isolated spikes or a gradual increase as labor became imminent. There was no relationship between a drop in BBT and the EDC. t-rj ...,- I.Q C 11 m I--' ttl 11 t1 III rt t-'- n tlj tIl 1-3 t"O III rt rt m t1 ::l en I'V W 24 Days since 37th week of gestation , I : of I, , ...~~ 98 ' ' .: . -". 86 Ix ,t...--i ' I 'It: i' , ) I i' I. I j I :1 l' 115 • .. : ; ~ '" , : : ~ : I' !. I I" . ·,1 :.: j 1 .. I , I ••• , j • • • • .. I i. 98 97 It; 96 ! !,.. t j, •• " ~ ~ :: ! :~ :~ 98 :":1\":: -----. --+~ ., l' .l: • j , 86 , Figure 2. I , i I !, BBT Decline 2-6 Days Before Labor I I i 25 Days since 37th week I ge~tati9n I I I .. X I I ·w 98 : f I . I I j •• 97 " '!'O i .. .£!. d U Itl· :: ffi J::: '0+J. I.e (/'I .+J #8 j.,... . · it!J · '0. : . 1::1 96 . , 1 : I :; r' . 'x ~ 98 I , I .' I·I 1 97 . --'rl-~~.-L:. : :.*;;).1 • i. ;, : i. i: :::!: I' . . I:: ~ : .. ! . .' .. . :":'.:. .... ~ .... L:..:.:..:.++.~-+-..;.. . . . . .-+-; .; ~ .' I;';::'" ! . 98 .:.~.. !. I ., j --7-:'-', 1 ... ! ! ---~-. · j ... j ! . ~ i :~t4nifi, na~led --'r ='aay'-cif -,.!=-.-+...;....j.-- I . I . ... I· . · ·I ..• i I : 97 . = :.. !i . #3j2 I .1 • . . ,;::. , . !J.. i . . Q). '0' ~.~~~~.~----~--~----~ OJ -- a i9- st· . "'--1 " · t · I .i ..Q,Q.-I . ~o· It1 a -H 0 o .,...!J 11: Figure 3. I ~ . j BBT Decline 16-19 Days Before Labor i i 26 98 97 Figure 4. BBT Decline 30 Days Before Labor CHAPTER V DICUSSSION Research Question One "Is there any change in BBT related to the spontaneous onset of labor in women at term?" The data offer some intriguing information, but no definitive answer to this question. Apparently some women demonstrate a significant drop in BBT at the end of pregnancy, but a relationship to the onset of labor is merely suggested rather than clearly defined. Research Question Two "Can observation of BBT's in women at term permit clinically useful prediction of the onset of spontaneous labor?" Two apparent patterns of BBT changes in half the women studied is not strong evidence to support routine BBT charting for the prediction of labor. That only half the women showed any changes at all makes BBT's no more predictive than many other traditionally observed signs and symptoms of impending labor. 28 Progesterone and Thermoregula'tion in Pregnancy The thermogenic effects of progesterone in menstrual cycles is observed in the upward shift in BBT's which occurs as plasma progesterone concentrations increase abruptly during the luteal phase of the cycle. When a pregnancy occurs, plasma progesterone concentration increases steadily from 23-54 ng/ml in the first trimester to 120-180 ng/ml in the third trimester (Tulchinsky & Ryan, 1980). However, the BBT does not appear to continue increasing as pregnancy progresses. The mean BBT of these subjects was actually LOWER than the BBT usually observed in women during the luteal phase of the menstrual cycle (97.71 0 vs > 0 98.0 F). The response of the hypothalamus to the thermogenic effects, of progesterone is apparently not related directly to plasma concentration, or we would expect elevations in BBT's to parallel increases in plasma progesterone concentration as pregnancy advances. Inconsistencies among BBT patterns and a lower-thanexpected mean BBT in these subjects offer a great challenge to interpretation of the role of progesterone in thermoregulation in women in late pregnancy. uterine irritability and labor occur in the presence of high or variable plasma progesterone concentrations, perhaps as 29 a result of alterations in the availability of either progesterone or its receptors in the myometrium. That only half the women studied demonstrated any change in BBT prior to labor suggests that analogous changes in thermoregulation by the hypothalamus, which might be observed as a change in BBT, apparently do not occur at the same time as the changes in myometrial activity. There are several possible explanations for the absence of a clearly defined change in BBT: 1) Perhaps progesterone does not withdraw from the hypothalamus, even though it may from the uterus and fetal membranes; 2) concentration of progesterone may decrease in hypothalamic tissues, but not below a threshhold necessary for an observable change in BBT; or, 3) progesterone does not withdraw from "any tissues, and an entirely different mechanism is responsible for the changes in uterine activity with the onset of labor. Consideration must also be given to those cases where a significant drop in BBT was followed by an elevation in temperature as labor approached. This observation invites speculation about other factors thought to be involved in both the onset of labor and body temperature. For example, there is compelling evidence that an increase in local tissue levels of prostaglandins is a common pathway for the activation 30 of normal labor, specifically PGE sky & Ryan, 1980). 2 and PGF2~ (Tulchin- PGE 2 is also apparently an active contributor to hypothalamic function and is involved in fever production (Veale, Cooper & Pittman, 1978). A common side effect experienced by women administered PGE 2 for induction of labor is transient elevation in temperature (Southern, 1976). Since prostaglandin release may occur with or without a decline in plasma progesterone (Tulchinsky & Ryan, 1980), elevations in temperature observed after a drop may be a reflection of prostaglandin activity as labor becomes imminent. The variability among individual temperature patterns seems to add to evidence that the onset of labor is a multifactorial process rather than the result of a singular metabolic pathway. CHAPTER VI SUMMARY The results of this investigation do not strongly support the observation of BBT's to predict the onset of labor. However, the discovery of two apparently distinct patterns of change in the BBT's of some women merits further investigation. The experiences of this researcher lead to several suggestions for improvement in future work with BBT's in late pregnancy: 1) Since so many women in this study delivered before charting began, initiation of BBT observations at 34 or 35 weeks' gestation would probably yield more information, and perhaps offer some insight into premature labors. 2) Oral temperatures are apparently just as accurate as vaginal temperatures, and have a higher compliance rate among subjects. 3) Selection of subjects from childbirth classes is both more efficient for recruitment and results in greater numbers of charts returned than with subjects 32 recruited individually from private prenatal visits. 3) The baseline B in the CUSUM test should be computed using the first 7 BBT readings, rather than the first 3, in order to establish a more representative baseline. APPENDIX A INSTRUCTIONS TO PARTICIPANTS 34 Instructions to Participants Thank you for participating in this study of basal body temperatures in women during the last few weeks of pregnancy. No one has carefully studied temperatures in pregnancy, so this study will add to our knowledge about physiological changes in women as labor approaches. The basal body temperature is the body's temperature at complete rest and is especially accurate when taken at the same time each day. Therefore, we ask that you follow these guidelines as closely as possible. 1. Take your temperature orally by inserting the basal body temperature thermometer provided to you into your mouth under your tongue. Leave the thermometer in your mouth for a full three minutes before reading the temperature. 2. Take your temperature after at least four hours consecutive sleep before beginning ANY activity; this will be first thing in the morning before rising for most women. Keep your thermometer at your bedside so you don't have to rise to get it. If, for some reason, your sleep was less than four hours in a row, or you had interrupted sleep, take your temperature anyway and make a notation in the comments area of your chart. For example, if you got up to the bathroom during the night, write Uto bathroom" and try to note the time. 3. Shake down your thermometer before going to sleep. Look at the morning's reading one more time to double check the accuracy of your charting. 4. You may wash your thermometer with soap and COLD water or alcohol. Generally, all you need to do is simply wipe the thermometer with a clean tissue or cloth after each use and store it in the container it came in. Do NOT wash the thermometer in warm or hot water. 5. There are some other things you will need to write in the comments area of your chart: a. b. c. Fever or illness Any medications or drugs other than vitamins or iron Anything you think might have affected your temperature 35 6. Please note that we need information about your labor and birth on the chart also. This is just as important as the daily temperatures. 7. If you have any questions or concerns, or something happens to your thermometer, please feel free to contact me at (801) 466-7982. APPENDIX B BASAL BODY TEMPERATURE CHART 37 Instructions for Charting To record the temperature for each day, place a solid dot on the line for that temperature in the middle of the box, like this: Begin charting on the date written at the top of the chart. This should be the day you complete 37 weeks of gestation since your last period. Write any comments in the long columns below the temperature for that day. It is VERY important that I have the following information as well for the study: 1. Regular, frequent contractions that were confirmed as true labor by an internal, cervical exam began at am/pm (time) on (date). - - ------ 2. Your bag of waters (underline) broke spontaneously/was broken artificially at am/pm (time) on ~~~----------------(date) . 3. You were admitted to the hospital or birth center at am/pm on 4. Your baby was born at am/pm on (underline appropriate descriptions) vaginal delivery/forceps/ cesarean. Reason for cesarean: ----- 5 •. Please list any medications or drugs received before or during labor not already charted in the comments area of your chart, including epidural anesthesia or pitocin to stimulate labor: name of medication time date 38 All this information will be kept confidential. Your chart will be identified by a code number. You may reach me at if you have any questions or concerns. Basal Body Temperature Chart Begin charting on_____________________________________________ Oat~ I'"., .t ."Ir 10 ~ I "'. , ..... , Temp. 4 .3· 2 '" f.-1- ..4-+-·+-·~·- - ... - - - .. ._. ..... - . .5 -- -- r- .- ._. '- _.- -- _. I· .. · j. . . . .- -.- 1-· .. '-- -- - I--f-- - .. - .-. f· 1- .. _' ... .. - .- '-r-- ,..... _. '-1-- ,-_._. .- - _. f- -f- 1--1-.- - __ ---I- _- - r-',- . '-1- --1-' 1-- .. - I-i-"- . .... 9qO~~_+~4_+-+-~-+~~4_+_~~_+~~+_+_~_+~~4_+_~~_+~~+_+_~_; .q S 7 .b 5 , .3 2 ...._. ---1-- I.. · . - - f - · · · .. ,. -1-'" r-'- !-- 1--- --f-- . - .......+-+--11---1· .. - +.. / - - 1_ir~-t· ,.. !--!--.- -- - r ._ .. r'" -- I ~ --I--I~-+-I--t- I"'" -- _. -- .. - . r .. ·.... --,._- ... '-i--ii-i--+ -- I- -- . .. '-- i' . - - - I- .. f- - .. - ,.- -r- 1--- --t--+-·-\-_·t"'"""1'-·1··.. --t- -1-+-t--1-.... ·-.. -1 -'11-' ' - r . -- .. r' -- -. '1- "'r'" . • .- • .- --1--+-+--1--1··· c·- -- . .. . 1-'1---' - 1- .-.~'. 98.0~~_+~+_+-~-+~+_+-~-+_r4_+_~_+_r4_+_~_+_r4_~~_+_r~+_~_+~ 9 .---~I_t_+_i··+ 1..-- --- - +--HHH-+-+++--t-+-t--rilR I- -'1--1'-+-+--+- - - 1 - ' - . f- '-.. .. r- r-7 :-- !-- r-- .-. 6 r- -1-"- --f-- .- I-r-- -. .5 . 1--... -- - f - ' - I - I - ' " . 4--f--t---l!--1_+-+-+-+-.. t - , .. - 1__ ' .3 "-'r-- -+-+"-i-1-'!-i. 2 J-~I---t-+-+'-i'- - 1 - I .. .. c- :-.--1" -r- c - I'H.O 1--11--+-+--1- .. comment -!--·--li-·f-I--·' . -_.. f-. - --- . r--- - -- f----- ---1-1- ,+ ..+""t-t .. _.- "-'r- ._- - - I ' - ., - 1-1- - - , C_ .. 1- . - - -t-if--t-+-++-I-' .. .. r- -- .. - I - ... I- +---I--!r-I---+.c-J----- --1--1- -- "- - "--i-I-" 1-- .- - - .. 1-- REFERENCES 40 Boroditsky, R.S., Reyes, F.I., Winter, J.S.D., & Faiman, C. Maternal serum estrogen and progesterone concentrations preceding normal labor. Obstetrics and Gynecology, June 1978, 51 (6),686-91. Burd, L.I. The relationship of mammary temperature to parturition in human subjects. American Journal of Obstetrics and Gynecology, June 1977,128 (3), 272-8. Concannon, P.W., Powers, M.E., Holder, W., & Hansel, W. Pregnancy and parturition in the bitch. Biology of Reproduction, 1977, ~, 517-526. Dufty, J.H. Determination of the onset of parturition in hereford cattle. Australian Veterinary Journal, March 1971, 47 (3), 77-82. Ewbank, R. The fall in rectal temperature seen before parturition in sheep. Journal of Reproduction and Fertility, 1969, 19, 569-571. Griesemer, R.A., & Gibson, J.P. The gnotobiotic dog. Laboratory and Animal Care, August 1963, 13 (4), 643-649. Goodlin, R.C. 1981. Personal communication. November 19, Hendrix, W.F., Kelley, K.W., Gaskins, C.T., & Bendel, R.B. Changes in respiratory rate and rectal temperature of swine near parturition. Journal of Animal Science, 1978, !2 (1), 188-191. Jones, D.E., & Knifton, A. Assessment of time of onset of parturition in goats by means of daily recording of rectal temperatures. The Veterinary Record, September 11, 1971, ~ (11), 300-302. King, G.J., Willoughby, R.A., & Hacker, R.R. Fluctuations in rectal temperature of swine at parturition. Canadian Veterinary Journal, 11arch 1972, 13 (3), 72-~ Kirk, R.W., McEnter, K., & Bentinck-Smith, J. Urogenital system diseases. In E.J. Catcott (Ed.), Canine medicine. Santa Barbara: American Veterinary Publications, 1968, p. 408. Littledike, E.T., Witzel, D.A., & Riley, J.L. Body temperature changes in sows during the periparturient period. Laboratory and Animal Science, October 1979, 41 ~ (5), 621-624. Long, D., Mezza, R., & Krakowka, S. Signs of impending parturition in the laboratory bitch. Laboratory and Animal Science, April 1978, ~ (2)., 178-181. Pritchard, J.A., & MacDonald, P.C. Williams obstetrics (16th ed). New York: Appleton-Century-Crofts,1980. Royston, J.P., & Abrams, R.M. An objective method for detecting the shift in basal body temperature in women. Biometrics, June 1980, ~, 217-224. Ruppenthal, G.C. & Goodlin, B.L. Body temperatures of Macaca nemestrina during pregnancy and parturition. American Journal of Primatology, 1981, l (3), (abstract), 329. Southern, E.M. Experience in the united States clinical trials of prostaglandins in obstetrics and gynecology. In Sultan M.M. Kavin (Ed.), Obstetric and gynecological uses of prostaglandins (congress proceedings). Baltimore: University Park Press, 1976, pp. 105-118. Tulchinsky, D., & Ryan, K.J. Maternal-fetal endocrinology. Philadelphia: W.B. Saunders Company, 1980. Varney, H. Nurse-midwifery. Boston: fic Publications, Inc., 1980. Blackwell Scienti- Veale, W.L., Cooper, K.E., & Pittman, Q.J. Prostaglandins action on central thermoregulation and fever: Ontogenetic aspects. In F. Coceani & P.M. Olley, (Eds.), Advances in prostaglandins and thromboxane research (Vol. 4). New York: Raven Press, 1978, pp. 199-213. Walsh, S.W., & Novy, M.J. Diurnal variations in plasma and amniotic fluid (AF) steroids before parturition. (Abstract) Scientific Sessions of the 27th Annual Meeting of the Society for Gynecologic Investigation, March 19-22, 1980, Denver, Colorado. Winfield, C.G., Makin, A.W., & Williams, A.H. Prediction of the onset of parturition in sheep_ Australian Veterinary Journal, December 1973, 49, 549-553. Weisz, L. The temperature phenomenon before parturition and its clinical importance. Journal of the American Veterinary Nedical Association, 1943, 102, 123.
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