Keywords

Bed rest, Cervical dilatation, Labor screening, Rest, Sensitivity and specificity, Time to delivery.

 

Authors

  1. Selby, Chris RNC
  2. Valencia, Sherry RN, BSN
  3. Garcia, Lindsay RN
  4. Keep, Denise RN, BSN
  5. Overcash, Jonnie RNC, BSN, MSN
  6. Jackson, Jasmin RN, BSN

Abstract

Purpose: Determine if bed rest or walking during a 1-hour labor check evaluation affects progression to delivery.

 

Study Design: Randomized controlled trial.

 

Methods: Convenience sample of nulliparous full-term, low-risk women with an initial negative exam for active labor (cervical dilatation < 4 cm; intact membranes) were randomly assigned to bed rest or walking for 1 hour prior to reassessment. Cervical dilatation and comfort level were evaluated before and after 1 hour of bed rest or walking. For patients who delivered within 24 hours, time to delivery was documented. Data were analyzed with Student's t-test and c2-test. Positive and negative predictive values were calculated for the 1-hour labor check evaluation as a screen for delivery within 24 hours (negative screen = no change in cervical dilatation after 1 hour; positive screen = >=1 cm change in cervical dilatation after 1 hour).

 

Results: Sixty-three participants were studied before and after a 1-hour period of bed rest (n = 32) or walking (n = 31). No differences were found between the groups in changes of cervical dilatation, time to delivery, number of women delivering within 24 hours, or maternal comfort after the 1-hour labor check evaluation. Predictive values of the 1-hour labor check evaluation to determine delivery within 24 hours were 88.2% (positive predictive value) and 54.3% (negative predictive value).

 

Clinical Implications: Cervical dilatation and time to delivery were similar for nulliparous, full-term, low-risk women regardless of activity level during a 1-hour, in-hospital labor check evaluation. The woman's preference can be used to determine activity level during a labor check evaluation. Positive 1-hour labor check evaluations were highly predictive of delivery within 24 hours. A negative 1-hour labor check evaluation, however, was not a good predictor of delivery within 24 hours.

 

Article Content

Toward the end of a pregnancy, it is not uncommon for women to experience uterine contractions that may or may not indicate the beginning of active labor. To ascertain whether labor has actually begun, labor and delivery (L&D) nurses assess the woman to determine the length and frequency of uterine contractions, presence of bloody show, status of membranes, and assessment of the cervix for signs of impending delivery (Cunningham, Leveno, Bloom, Hauth, Rouse, & Sponge, 2010).

  
Figure. No caption a... - Click to enlarge in new windowFigure. No caption available.

When the initial evaluation for active labor is inconclusive (cervical dilatation <4 cm, membranes intact, contractions are mild or irregular), some L&D units do a second evaluation after a time period to determine if cervical dilatation is actually progressing. Results of this labor check evaluation are used to guide clinicians' decisions on whether delivery within 24 hours is predicted and whether expectant mothers should remain in the hospital or be sent home. At our facility, if cervical dilatation is similar at the end of a 1-hour labor check evaluation, membranes are intact and contractions still infrequent/irregular, then clinicians believe delivery within the next 24 hours is unlikely and the woman is sent home. If cervical dilatation increases by >=1 cm after the 1-hour labor check evaluation, then delivery within the next 24 hours is thought to be likely, and the woman is admitted to the hospital for delivery.

 

During the designated time period between the two cervical examinations, two activity levels are used: walking or bed rest. The decision to have the mother walk or rest is based on clinician or mother preference, rather than evidence that a particular activity level is best for the 1-hour labor evaluation. No randomized, controlled trials have compared these two activity levels during labor check evaluations to determine if the level of activity affects the outcome of the labor check evaluation.

 

Although the underlying rationale for recommending one type of activity level over the other during a 1-hour labor check evaluation is not known, it may be a logical extension of some clinicians' beliefs that activity levels during active labor affect time to delivery. Prior studies of activity levels during active labor have compared the effects of bed rest to ambulation or upright positioning during the entire first and/or second stages of labor. Meta-analyses of positioning studies during the first stage of labor found reductions in the length of labor (Lawrence, Lewis, Hofmeyr, Dowswell, & Styles, 2009; Souza, Miquelutti, Cecatti, & Makuch, 2006) but no differences in length of labor due to activity level in the second state of labor (Gupta & Hofmeyr, 2004; Roberts, Algert, Cameron, & Torvaldsen, 2005). Those authors suggested that women should be allowed to choose the position they find most comfortable during the labor because activity level did not dramatically alter time to delivery, and complications were similar for the two activity levels.

 

As prior research suggests that activity levels have no clinical significance on outcomes during active labor, we hypothesized that different activity levels during a 1-hour labor check evaluation would not change the rate of cervical dilatation and thus progression to a positive 1-hour labor check. If the activity level during the 1-hour labor check evaluation does not influence the rate of cervical changes, then women should be allowed to select their activity level based on their preference and/or comfort level and not be based on clinician biases or hospital routines.

 

The primary purpose of this study was to compare two different levels of activity (either walking or bed rest) during a 1-hour labor check evaluation on cervical changes and progression to delivery in full-term, nulliparous women with low-risk pregnancies. A secondary purpose of the study was to determine the mother's comfort level with rest or walking during the 1-hour labor check evaluation. Another purpose of the study was to determine how well the 1-hour labor check evaluation predicted delivery within the next 24 hours. As the outcome from the 1-hour labor check is used by some clinicians to determine if women are admitted to the hospital or sent home, it is critical to know how well this procedure works as a screening tool of impending delivery.

 

Study Design and Methods

This study was conducted in a high-risk, perinatal unit with over 2,000 deliveries per year within a 564-bed community-based hospital in the Midwest region of the United States. Approval to conduct the study was obtained from the institution's investigational review board prior to data collection.

 

Study Design

This was a randomized controlled trial to compare two different activity levels (bed rest or walking) during a 1-hour labor check evaluation. Random assignment was done with a computer random number generator, with concealment of group allocation by sealed, opaque envelopes maintained until after baseline data collection was completed, just prior to beginning the rest or walking period.

 

The primary outcome variables of this study were changes in cervical dilatation and the occurrence of delivery within 24 hours after the 1-hour labor check evaluation. Secondary outcome variables were the effect of activity level on comfort during the 1-hour labor check evaluation and the sensitivity and specificity of the 1-hour labor check evaluation to predict delivery within the next 24 hours. We used the definition of a positive and negative labor check evaluation result based on the criteria used at our institution: when the initial evaluation for the presence of active labor is inconclusive, a change from baseline values in cervical dilatation of >=1 cm after the 1 hour period indicates a positive labor check, with delivery likely within 24 hours. No change in cervical dilatation over the 1-hour period is a negative labor check and occurrence of delivery within 24 hours is not likely.

 

Instruments

Patient comfort level was assessed between uterine contractions using a visual analog scale (VAS) with a 100-mm vertical line. VAS scores have previously been found to be valid and reliable methods to assess clinical symptoms such as pain, comfort, dyspnea, and fatigue (Bijur, Silver, & Gallagher, 1998; Flaherty, 1996; Goncalves, Wiezel, Goncalves, Hebling, & Sannomiya, 2009; Lee, Hicks, & Nino-Muncia, 1991; Lee & Keickhefer, 1989; Mayberry, Gennaro, Strange, Williams, & De, 1999).

 

Each patient's comfort level was assessed at two time points: at baseline-prior to random assignment to bed rest or walking-and after 1 hour of bed rest or walking. In the current study, the lowest endpoint on the VAS was anchored by the words "Extremely Comfortable" and the highest endpoint was anchored by the words "Extremely Uncomfortable." The participant was directed to make a horizontal mark through the point on the vertical line that indicates how comfortable or uncomfortable she was feeling at that moment. Prior to completing the VAS for the study, each participant practiced marking a VAS once under supervision to verify that they understood how to mark the VAS properly. Scoring of the VAS was conducted at a later time by measuring in millimeters from the lowest end of the vertical line to the intersection of the participant's mark on the vertical line. Scores on the VAS can range from 0 to 100 mm, with higher scores indicating higher levels of discomfort.

 

Sample Selection

Participants in this study consisted of a convenience sample of 63 nulliparous full-term, low-risk women with an initial negative screen for active labor. Inclusion criteria were ability to speak and understand English, pregnancies of 37 to 42 weeks of gestation, nulliparous, singleton gestation, cephalic presentation, intact amnion, less than 4 cm cervical dilatation, blood pressure less than 140 mmHg systolic and 90 mmHg diastolic, and a category I fetal heart rate tracing (Macones, Hankins, Spong, Hauth, & Moore, 2008; Lyndon & Usher, 2009). Exclusion criteria included patients who would be unable to walk for a 1-hour period. Sample size (N = 63) was based on power analysis for two groups using Student's t-test, with an effect size of 0.6 (moderate) to achieve a power of 0.80 and a = 0.05 (Cohen, 1977; Faul & Erdfleder, 2010).

 

Study Procedure

Participants were randomly assigned to two different activity levels during a 1-hour evaluation period for active labor until data collection was completed on a total of 63 women. To ensure consistency in recruitment and data collection, all investigators were trained on the study methods. The study was presented to women who met the eligibility criteria by one of the study investigators after their arrival on the inpatient L&D unit for active labor evaluation. After obtaining informed consent, investigators performed baseline assessments, including demographic data and women's baseline comfort level on the VAS. A vaginal examination was then performed by one of the study investigators to determine cervical dilatation, effacement, and station. All study investigators were experienced L&D nurses, who routinely perform vaginal examinations for evaluation for active labor and used standardized techniques for determining cervical dilatation (Cunningham et al., 2010). To control for measurement error, vaginal examinations before and after the rest or walking period were performed by the same investigator.

 

Following baseline assessment, participants were then randomly assigned to the bed rest or walking group. Participants assigned to the bed rest group were instructed to remain in bed for 1 hour, with the exception of short trips to the bathroom. They were told to assume whatever position in the bed they desired, which could be supine, lateral, or a sitting position. Participants assigned to the walking group were instructed to walk for 1 hour, in and around the nursing unit. As investigators would not be able to visually observe participants during that period, a pedometer (GOWALKING, Model number GW2795GN, Sportline, Inc, Hazleton, PA) was attached to each participant in the walking group to verify that walking did occur during the 1-hour evaluation period.

 

After the 1-hour period of bed rest or walking, participants were asked to rate their comfort level on a VAS and then indicate whether they would have preferred bed rest or walking for the previous hour. A vaginal examination was performed to determine cervical dilatation. L&D room records were reviewed by an investigator to determine the total number of participants who delivered within 24 hours of the completion of the 1-hour intervention period (bed rest or walking).

 

Data Analysis

Data were summarized using descriptive statistics. Student's t-test was used to determine differences between the two groups for changes in cervical dilatation and comfort scores. The level of significance was set at p < .05.

 

Based on institutional criteria, for study purposes we defined a change in cervical dilatation of at least 1 cm after the 1-hour labor check evaluation as a positive labor check, indicating a high likelihood of delivery within 24 hours. Sensitivity (number of true positives/[true positives + false negatives]) was calculated to determine the proportion of positive evaluations for active labor that were correctly identified. Specificity (number of true negatives/[true negatives + false positives]) was calculated to determine the proportion of negative evaluations for active labor that were correctly identified.

 

Using standard formulas (Kirkwood & Sterne, 2003; Larsen, 1986), positive predictive value was calculated for the proportion of patients with a positive 1-hour labor check evaluation (at least a 1-cm change in cervical dilatation) who delivered within the next 24 hours (number of true positives/[true positives + false positives]). Negative predictive value was calculated for the proportion of patients with a negative 1-hour labor check evaluation (no change in cervical dilatation) who did not deliver within the next 24 hours (number of true negatives/[false negatives + true negatives]).

 

Results

Study enrollment took place over an 18-month period (October 2007-March 2009), occurring on all shifts and only when investigators were available for study enrollment. A total of 63 mothers consented to participation in this study, with all 63 enrolled participants completing the study (Figure 1). Thirty-two participants were assigned to bed rest for 1 hour, and 31 participants walked for 1 hour. Prior to implementing the 1-hour rest or walking period, age and labor characteristics were similar for the two groups (Table 1).

  
Figure 1 - Click to enlarge in new windowFigure 1. Flow Diagram of Randomized Controlled Trial of Activity Level During Evaluation of Active Labor in Full-Term, Nulliparous, Low-Risk Pregnant Women.
 
Table 1 - Click to enlarge in new windowTable 1. Baseline Characteristics of 63 Nulliparous, Low-Risk Pregnant Women of 37 to 42 Weeks of Gestation Prior to 1-hour Period of Rest or Walking for Labor Check Evaluation

The time spent walking or resting in bed during the 1-hour evaluation period was similar for both groups (Table 2) (p > .05). Pedometer measures validated that all participants in the walking did walk during the 1-hour period (range: 400-4,317 steps; mean +/- SD = 1,633 +/- 1,008 steps).

  
Table 2 - Click to enlarge in new windowTable 2. Changes in Cervical Dilatation and Comfort Level in 63 Nulliparous, Low-Risk Pregnant Women of 37 to 42 Weeks of Gestation After Bed Rest or Walking During a 1-hour Labor Check Evaluation

The average change in cervical dilatation after the 1-hour labor check evaluation period was an increase of 0.38 cm (+/- .6) and 0.33 cm (+/- .5) for the bed rest and walking groups, respectively (Table 2). Fifteen participants had >=1 cm increase in cervical dilatation (n = 8 rest in bed group; n = 7 walking group). No statistical differences were found between bed rest and walking for either of the outcome variables. Changes in effacement and station after the 1-hour labor check were similar and nonsignificant for the bed rest and walking groups (effacement: 0.93 +/- 3.7 and 0.97 +/- 5.1, respectively; station: 0.03 +/- 0.2 and 0.04 +/- 0.3, respectively).

 

Of the 63 participants, 57% (n = 36) delivered within 24 hours after the 1-hour labor check evaluation. In participants on bed rest for 1 hour, 53% (n = 17) delivered within 24 hours. In participants who walked for 1 hour, 61% (n = 19) delivered within 24 hours. The c2 analysis found no difference between the groups for delivery within 24 hours ([chi]2 = 0.43, df = 1, p = .52). The average length of time to delivery for those who delivered within 24 hours was 10.2 +/- 4.3 and 11.6 +/- 4.3 hours after bed rest or walking, respectively (t = -0.97, df = 33, p = .34). Forty-one participants had no change in cervical dilatation after 1 hour of bed rest or walking (n = 21 in bed rest group; n = 20 in walking group), with slightly less than half of them delivering within 24 hours after the 1-hour labor check evaluation (n = 17, 42%).

 

The sensitivity and specificity of a 1-hour labor check result to correctly screen for delivery within 24 hours are presented in Table 3. The positive predictive value was 88.2%, indicating that when there is a 1 cm or more change in cervical dilatation after the 1-hour labor check evaluation (positive result), delivery within 24 hours would be correctly predicted 88% of the time. The negative predictive value was 54.3%, indicating that a negative result after the 1-hour labor check evaluation (<1 cm cervical dilatation change), no delivery within 24 hours would only be correctly predicted 54% of the time.

  
Table 3 - Click to enlarge in new windowTable 3. Sensitivity and Specificity of the Results of a 1-hour Labor Check Evaluation to Identify Delivery Within 24 Hours in 63 Nulliparous, Low-Risk Pregnant Women of 37 to 42 Weeks of Gestation

Changes in comfort scores after the 1-hour labor check evaluation period were small and similar in the walking and bed rest groups (Table 2). After 1 hour of bed rest or walking, participants were asked to rate their preference for walking or bed rest. Thirty-four participants (54% of the total sample) preferred to walk (n = 17 in each group), whereas 17 participants (27%) preferred to rest (n = 9 in bed rest group; n = 8 in walking group), and 12 participants (32%) had no preference (n = 6 in each group). There was no difference in preference between those who actually walked or rested ([chi]2 = 0.04, df = 1, p = .98).

 

Clinical Implications

Results of our study found there was no difference in cervical dilatation changes or delivery within 24 hours for those who rested or walked during the a 1-hour labor check evaluation, indicating that activity level did not advance or slow cervical changes or delivery. These results should encourage clinicians to allow women to select their preferred activity level during a 1-hour labor check evaluation, rather than prescribing rest or walking based on clinician biases or hospital routines. When asked about their preference, slightly more than half of the participants preferred walking rather than bed rest during a 1-hour labor check evaluation.

 

The rationale for our institution's 1-hour labor check evaluation is to determine if expectant women whose initial evaluation for active labor is inconclusive are actually likely to deliver within the next 24 hours. If delivery is thought to be unlikely to occur within the next 24 hours, women are usually sent home for admission at a later time. Our study results indicate that a positive result on the 1-hour labor check evaluation (>=1 cm change in cervical dilatation) is a good predictor of delivery within the next 24 hours. A negative result (<1 cm change in cervical dilatation), though, was not a good predictor. Our findings suggest that a negative 1-hour labor check evaluation is not a good indicator for deciding if women should be sent home or not.

 

Prior to conducting this study, vaginal examinations to evaluate patients for active labor were often performed by different clinicians based on their availability at the time. During this study, however, the same investigator was required to perform both vaginal examinations for the 1-hour labor check evaluation. Investigators anecdotally noticed improved nurse-patient relationships and had more confidence in the results of the two vaginal examination measurements when performed by the same person, opposed to their clinical experience with having different clinicians doing the examinations before and after the 1-hour time period. The study investigators, who are also members of the unit nursing staff, recommended that future patient care assignments for 1-hour labor check evaluation should be consistent throughout their stay on the unit. In fact, as a result of this study, on most shifts one nurse is designated to perform all the 1-hour labor check evaluations.

 

Limitations

This study only evaluated English-speaking, full-term, low-risk pregnant women between 37 and 42 weeks of gestation. Whether similar results would be found in women of other ethnicities, multiparous women, and/or women with higher risk pregnancies is not known. Future studies should evaluate the impact of bed rest or walking during labor check evaluations in other patient populations and determine the predictive value of 1-hour labor check evaluation as a screening tool for delivery within 24 hours.

 

Another limitation of this study is that only one time period for the activity level was studied: 1 hour. This time period was selected because it represented the time period used at our facility for the labor check evaluation. It is possible that a longer period for the labor check evaluation would lead to different results. Future studies should evaluate longer time periods for activity.

 

Another limitation of this study is the criteria used by our facility to define a positive labor check as being a cervical dilatation of >=1 cm. Other institutions may have different criteria for a positive labor check, which could lead to different results. Given the negative predictive value of the labor check found in this study, future studies should examine if the use of additional criteria besides cervical dilatation could improve negative predictive values.

 

Because of the subjective nature of evaluating cervical dilatation, reliability of this outcome variable may be called into question. To minimize subjective measurement errors, we required the same investigator to perform both vaginal examinations required for the 1-hour labor check evaluation in each woman. Another limitation of the study was our inability to blind the investigators performing vaginal examinations from the participants' group assignment, which could have biased the study results. Future studies should attempt to blind the individuals conducting the vaginal examinations from group assignment to decrease the likelihood of investigator bias.

 

Conclusions

Changes in cervical dilatation and time to delivery were similar for nulliparous, full-term, low-risk women who were on bed rest or walked during a 1-hour in-hospital evaluation. The woman's preference can be used to determine activity level during an in-hospital, labor check evaluation. This study found that the result of a positive 1-hour labor check evaluation was highly predictive of delivery within 24 hours. A negative 1-hour labor check evaluation, however, failed to adequately predict that delivery would not occur within 24 hours.

 

Acknowledgment

Special thanks to Marianne Chulay, RN, PhD, FAAN, for assistance with study design, analysis, and manuscript preparation.

 

Suggested Clinical Nursing Implications

 

* Based on the results of this study, for in-hospital full-term, nulliparous women evaluated in an L&D unit for the presence of active labor, it does not make a difference in cervical dilatation if they walk or rest during the 1-hour labor check evaluation. Rather than requiring mothers to walk or rest during this period, clinicians should allow women to determine their activity level based on their preference. The vast majority of the women in this study stated their preference would be to walk during the 1-hour period.

 

* When the initial 1-hour labor check evaluation is inconclusive (cervical dilatation <4 cm; membranes intact; mild or irregular contractions), having a change in cervical dilatation of >=1 cm after a 1-hour period labor check evaluation ("positive labor check") is highly predictive of delivery within the 24 hours. Conversely, having a "negative labor check" (<1 cm change in cervical dilatation) is a poor predictor of impending delivery within 24 hours. Many of the women in this study with a negative labor check went on to deliver within 24 hours. If women are sent home after a negative labor check, they should be cautioned that a negative result is not conclusive, and they may actually deliver in the next 24 hours.

 

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