Early signs and symptoms of preterm labor Michael Katz, MD, Karen Goodyear, MD, and Robert K. Creasy, MD San Francisco, California, and Houston, Texas Patient and staff education concerning the subtle signs and symptoms that precede a clinical diagnosis of preterm labor have not been well established. Therefore we interviewed 100 patients for the presence or absence of various symptoms and signs during the 7 days preceding diagnosis of preterm labor. An additional 100 patients without preterm labor matched for gestation were chosen at random as control subjects. A history of increased uterine contractions, menstrual cramps, constant backache, constant pelvic pressure, increased amount and consistency and color change of vaginal discharge, and increased frequency of urination were present with a statistically significant higher frequency in patients with preterm labor compared with controls. Twenty-nine percent of patients did not report any uterine contractions and only half described them as painful. Fewer than 50% of the women reported contractions as frequently as every 10 minutes or more. (AM J OBSTET GYNECOL 1990;162:1150-3.)
Key words: Pre term labor, signs, symptoms Despite the availability of tocolytic agents there has been no appreciable decrease in the incidence of preterm births in the United States. Over the last several years it has become evident that attempts to reduce this incidence must in part focus on improving the effectiveness of tocolysis through an earlier detection of preterm labor. Several programs that focused on patient and staff education about the putative signs and symptoms of preterm labor have been established; some, but not all, have had significant success. I -4 However, the validity of the signs and symptoms of preterm labor used for identifying the onset of labor and their predictive values have not yet been established and are the subject of this article. In this prospective study a comparison between the frequency of several signs and symptoms among patients who developed preterm labor and that observed among gestational-age-matched patients with term labor was undertaken.
Two hundred patients who agreed to participate in this study were interviewed by one of the authors (K. G.). The structured interview focused only on questions concerning the presence, duration, and characteristics of nine symptoms thought to be possibly associated with preterm labor (Table I). Specifically, pa-
tients were asked to report if any of the signs and symptoms occurred during the last 7 days either before admission (for inpatients with preterm labor) or before the interview (for outpatients without preterm labor). Of the 200 participants, 100 had a confirmed diagnosis of preterm labor. The interviews of these women took place after the initial preterm labor episode was adequately controlled with parenteral treatment (usually within 48 hours of admission). The diagnosis of preterm labor was made in the presence or regular uterine contractions leading to progressive cervical dilatation and effacement before 37 completed gestational weeks. No patients interviewed who met these criteria were excluded. Cervical status was assessed by digital palpation and documented for all such patients on admission. An additional 100 patients matched for gestational age who did not have pre term labor were interviewed in the outpatient clinic by the same interviewer in an identical fashion to that described above. The distribution of clinical characteristics among the patients in each of the groups is given in Table II. Comparisons between the group of patients who had preterm labor and those who had term labor were done with X2 analyses. In addition, the relationships between cervical status on admission for pre term labor and duration of symptoms were determined by analyzing the correlation coefficient.
From the Department of Obstetrics, Gynecology and Reproductive Sciences, The University of California and Children's Hospital of San Francisco, and The University of Texas Medical School at Houston. Receivedfor publication October 3, 1989; accepted February 6, 1990. Reprint requests: Robert K. Creasy, MD, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Texas Medical School-Houston, 6431 Fannin, Suite 3.286, Houston, TX 77030. 6/1/19915
Results The odds ratio and significance levels for the nine categories of signs and symptoms are detailed in Table III. The signs most frequently reported by women with the diagnosis of preterm labor were uterine contractions (71%), pelvic pressure (50%), backache (47%), increased amount of vaginal discharge (45%), and menstrual-like cramps (43%). Of the 71 subjects with
Material and methods
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pre term labor who perceived the presence of contractions, 26 (37%) reported them at a frequency of less than five contractions per hour. Although pelvic pressure and backache were more frequently reported by women who developed preterm labor, the differences were not significant. However, when asked to characterize these symptoms as constant or intermittent, the difference became significant. Women with preterm labor felt constant pelvic pressure and constant backache more often than their counterparts who labored at term (Table III). Although uterine contractions were the most frequently encountered symptom in women who developed preterm labor, of special interest is the fact that almost a third of these women did not report any uterine contractions. Of those patients with contractions or menstrual cramps who were asked if they would characterize them as painful, only 55% felt pain with contractions and 53% with menstrual cramps. Nineteen percent reported neither contractions nor menstrual-like cramps, and 15% reported no contraction, menstrual-like cramps, or abdominal intestinal cramps. Only two of the women who developed preterm labor reported none of the nine symptoms. The durations of certain symptoms that were found to be significantly more frequent with preterm labor were correlated with cervical status on admission for women with preterm labor. None of these relationships were significant. As shown in Table IV, previous labor experience had no effect on frequency with which symptoms were reported by women in preterm labor. The multiparous women more frequently reported diarrhea, but the numbers were small and the clinical significance of this observation is questionable. In addition, there was no significant difference between multiparous and nulliparous women in the time interval between onset of symptoms and presentation for medical evaluation (mean time interval, 166.9 ± 185.98 hours and 159.1 ± 215.11 hours, respectively).
Comment In recent years there has been an increased emphasis on the need to establish the diagnosis of pre term labor early.1.5 Because many of the warning signals are very subtle, several investigators established preterm birth prevention programs that focused on patient and staff education regarding the signs and symptoms of preterm labor. Many of these programs were successful, but the frequency with which these signs and symptoms were encountered and their discriminatory values have never before been established. In an attempt to analyze our data further, we calculated the sensitivities, specificities, and predictive values for the eight signs and symptoms most significantly associated with preterm
1151
Table I. Question list of signs and symptoms Uterine contractions Frequency Associated with pain Menstrual cramps Associated with pain Adbominal-intestinal cramps Backache Constant or intermittent Diarrhea Change in vaginal discharge Amount Consistency Color Change in urinary habits Frequency Burning sensation Change in frequency of fetal movement
Table II. Characteristics of cases and controls Preterm labor (n
Age (yr) Gestational age (wk) Nulliparous Twins Previous preterm labor Previous pre term birth
= 100)
Term labor (n
= 100)
26.03 ± 5.97 30.82 ± 3.72
26.61 ± 33 29.82 ± 4.11
52 12 19
41 3 12
17
10
Values represent mean ± SD.
labor (Table V). It is evident that all eight have excellent positive predictive values in excess of 80%. This would thus indicate that the appropriate response to complaints that include any of the above characteristics in patients known to be at high risk of preterm labor is a prompt evaluation to rule out the presence of pre term labor. Conversely, the data in Table V also indicate that the sensitivities for all symptoms, except contractions, are below 50%; thus relying only on the presence of signs and symptoms may help identify fewer than half the patients who ultimately have pre term labor. A potentially significant limitation of retrospective questioning as done in this study cannot be ignored. Patients who have been diagnosed as having preterm labor and those who are at risk for this condition may be more likely to recall the presence of signs and symptoms of preterm labor than those women who have normal gestations. Furthermore, retrospective reporting of symptoms and signs in response to questioning is not identical to prospective, patient-initiated reporting. It can be expected that further decline in sensitivity would occur in a prospective study. This is primarily because pregnant women are more likely to be distracted in the out-of-hospital environment. Further-
1152
Katz, Goodyear, and Creasy
May 1990 Am ] Obstet Gynecol
Table III. Cases and control subjects: Presence and significance of symptoms Cases (No. 1100)
Controls (No. 1100)
71 45 20 6 43 17 47 25 22 50 20 30
5 0 3 2 5 2 20 1 19 34 3 31
45 1 28 10 34
Uterine contractions Every 10 minutes or more frequent 1-4 per hour Every few hours Menstrual cramps Abdominal-intestinal cramps Backache Constant Intermittent Pelvic pressure Constant Intermittent Vaginal discharge Increased amount Decreased amount Increased consistency Decreased consistency Change in color Urinary habits Increased frequency Decreased frequency Burning sensation Fetal movement Increased movement Decreased movement Diarrhea
Odds ratio
Significance
46.52
Key words: Pre term labor, signs, symptoms Despite the availability of tocolytic agents there has been no appreciable decrease in the incidence of preterm births in the United States. Over the last several years it has become evident that attempts to reduce this incidence must in part focus on improving the effectiveness of tocolysis through an earlier detection of preterm labor. Several programs that focused on patient and staff education about the putative signs and symptoms of preterm labor have been established; some, but not all, have had significant success. I -4 However, the validity of the signs and symptoms of preterm labor used for identifying the onset of labor and their predictive values have not yet been established and are the subject of this article. In this prospective study a comparison between the frequency of several signs and symptoms among patients who developed preterm labor and that observed among gestational-age-matched patients with term labor was undertaken.
Two hundred patients who agreed to participate in this study were interviewed by one of the authors (K. G.). The structured interview focused only on questions concerning the presence, duration, and characteristics of nine symptoms thought to be possibly associated with preterm labor (Table I). Specifically, pa-
tients were asked to report if any of the signs and symptoms occurred during the last 7 days either before admission (for inpatients with preterm labor) or before the interview (for outpatients without preterm labor). Of the 200 participants, 100 had a confirmed diagnosis of preterm labor. The interviews of these women took place after the initial preterm labor episode was adequately controlled with parenteral treatment (usually within 48 hours of admission). The diagnosis of preterm labor was made in the presence or regular uterine contractions leading to progressive cervical dilatation and effacement before 37 completed gestational weeks. No patients interviewed who met these criteria were excluded. Cervical status was assessed by digital palpation and documented for all such patients on admission. An additional 100 patients matched for gestational age who did not have pre term labor were interviewed in the outpatient clinic by the same interviewer in an identical fashion to that described above. The distribution of clinical characteristics among the patients in each of the groups is given in Table II. Comparisons between the group of patients who had preterm labor and those who had term labor were done with X2 analyses. In addition, the relationships between cervical status on admission for pre term labor and duration of symptoms were determined by analyzing the correlation coefficient.
From the Department of Obstetrics, Gynecology and Reproductive Sciences, The University of California and Children's Hospital of San Francisco, and The University of Texas Medical School at Houston. Receivedfor publication October 3, 1989; accepted February 6, 1990. Reprint requests: Robert K. Creasy, MD, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Texas Medical School-Houston, 6431 Fannin, Suite 3.286, Houston, TX 77030. 6/1/19915
Results The odds ratio and significance levels for the nine categories of signs and symptoms are detailed in Table III. The signs most frequently reported by women with the diagnosis of preterm labor were uterine contractions (71%), pelvic pressure (50%), backache (47%), increased amount of vaginal discharge (45%), and menstrual-like cramps (43%). Of the 71 subjects with
Material and methods
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Preterm labor-Signs, symptoms
Volume 162 Number 5
pre term labor who perceived the presence of contractions, 26 (37%) reported them at a frequency of less than five contractions per hour. Although pelvic pressure and backache were more frequently reported by women who developed preterm labor, the differences were not significant. However, when asked to characterize these symptoms as constant or intermittent, the difference became significant. Women with preterm labor felt constant pelvic pressure and constant backache more often than their counterparts who labored at term (Table III). Although uterine contractions were the most frequently encountered symptom in women who developed preterm labor, of special interest is the fact that almost a third of these women did not report any uterine contractions. Of those patients with contractions or menstrual cramps who were asked if they would characterize them as painful, only 55% felt pain with contractions and 53% with menstrual cramps. Nineteen percent reported neither contractions nor menstrual-like cramps, and 15% reported no contraction, menstrual-like cramps, or abdominal intestinal cramps. Only two of the women who developed preterm labor reported none of the nine symptoms. The durations of certain symptoms that were found to be significantly more frequent with preterm labor were correlated with cervical status on admission for women with preterm labor. None of these relationships were significant. As shown in Table IV, previous labor experience had no effect on frequency with which symptoms were reported by women in preterm labor. The multiparous women more frequently reported diarrhea, but the numbers were small and the clinical significance of this observation is questionable. In addition, there was no significant difference between multiparous and nulliparous women in the time interval between onset of symptoms and presentation for medical evaluation (mean time interval, 166.9 ± 185.98 hours and 159.1 ± 215.11 hours, respectively).
Comment In recent years there has been an increased emphasis on the need to establish the diagnosis of pre term labor early.1.5 Because many of the warning signals are very subtle, several investigators established preterm birth prevention programs that focused on patient and staff education regarding the signs and symptoms of preterm labor. Many of these programs were successful, but the frequency with which these signs and symptoms were encountered and their discriminatory values have never before been established. In an attempt to analyze our data further, we calculated the sensitivities, specificities, and predictive values for the eight signs and symptoms most significantly associated with preterm
1151
Table I. Question list of signs and symptoms Uterine contractions Frequency Associated with pain Menstrual cramps Associated with pain Adbominal-intestinal cramps Backache Constant or intermittent Diarrhea Change in vaginal discharge Amount Consistency Color Change in urinary habits Frequency Burning sensation Change in frequency of fetal movement
Table II. Characteristics of cases and controls Preterm labor (n
Age (yr) Gestational age (wk) Nulliparous Twins Previous preterm labor Previous pre term birth
= 100)
Term labor (n
= 100)
26.03 ± 5.97 30.82 ± 3.72
26.61 ± 33 29.82 ± 4.11
52 12 19
41 3 12
17
10
Values represent mean ± SD.
labor (Table V). It is evident that all eight have excellent positive predictive values in excess of 80%. This would thus indicate that the appropriate response to complaints that include any of the above characteristics in patients known to be at high risk of preterm labor is a prompt evaluation to rule out the presence of pre term labor. Conversely, the data in Table V also indicate that the sensitivities for all symptoms, except contractions, are below 50%; thus relying only on the presence of signs and symptoms may help identify fewer than half the patients who ultimately have pre term labor. A potentially significant limitation of retrospective questioning as done in this study cannot be ignored. Patients who have been diagnosed as having preterm labor and those who are at risk for this condition may be more likely to recall the presence of signs and symptoms of preterm labor than those women who have normal gestations. Furthermore, retrospective reporting of symptoms and signs in response to questioning is not identical to prospective, patient-initiated reporting. It can be expected that further decline in sensitivity would occur in a prospective study. This is primarily because pregnant women are more likely to be distracted in the out-of-hospital environment. Further-
1152
Katz, Goodyear, and Creasy
May 1990 Am ] Obstet Gynecol
Table III. Cases and control subjects: Presence and significance of symptoms Cases (No. 1100)
Controls (No. 1100)
71 45 20 6 43 17 47 25 22 50 20 30
5 0 3 2 5 2 20 1 19 34 3 31
45 1 28 10 34
Uterine contractions Every 10 minutes or more frequent 1-4 per hour Every few hours Menstrual cramps Abdominal-intestinal cramps Backache Constant Intermittent Pelvic pressure Constant Intermittent Vaginal discharge Increased amount Decreased amount Increased consistency Decreased consistency Change in color Urinary habits Increased frequency Decreased frequency Burning sensation Fetal movement Increased movement Decreased movement Diarrhea
Odds ratio
Significance
46.52
