Inhibition of uterine contractility in labor

Uterine Contraction Parameters Before and During the Pre-Epidural Fluid Bolus: A Pilot Study

BACKGROUND

The first stage of labor is significantly longer with epidural analgesia use, implying an alteration in uterine contractility. Although the pre-epidural fluid bolus is used with every epidural and affects as many as 80% of laboring women, its effects on uterine contraction parameters are unknown.

DESIGN

Using a retrospective descriptive repeated measures design, we compared uterine contraction parameters including frequency, duration, peak intensity, resting tone, and Montevideo units at baseline and during the intravascular pre-epidural fluid bolus (Bolus) epochs for healthy laboring women at term gestation undergoing augmentation or induction.

METHOD

Contraction parameters were compared using data from fetal monitor strips with intrauterine pressure catheter instrumentation.

RESULTS

No significant differences were found between epochs for women receiving constant Pitocin dosages (n = 10) using Wilcoxon signed rank tests at .05 α level, but all parameters trended in the direction of improved contractility except frequency, which was unchanged.

CONCLUSIONS

These pilot study findings do not support the proposal that the pre-epidural fluid bolus is a contributor to decreased uterine contractility in any parameter. It is possible that the bolus improved myometrial perfusion and metabolic function in the contracting and resting states in less hydrated women.

Hydration for treatment of preterm labour

BACKGROUND

Hydration has been proposed as a treatment for women with preterm labour. Theoretically, hydration may reduce uterine contractility by increasing uterine blood flow and by decreasing pituitary secretion of antidiuretic hormone and oxytocin.

OBJECTIVES

To evaluate the effectiveness of intravenous or oral hydration to avoid preterm birth and its consequences in women with preterm labour.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 September 2013) and bibliographies of relevant papers.

SELECTION CRITERIA

Randomised controlled trials, including women with a viable pregnancy less than 37 completed weeks' gestation and presenting with preterm labour, comparing intravenous or oral hydration with no treatment. The intervention might or might not be associated with bed rest. Studies comparing tocolytic drugs with intravenous fluids used in the control group as a placebo were not included in this review.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the reports, to determine if the study met the inclusion criteria and to evaluate the methodological quality. Data were extracted independently by two of the review authors. The results were expressed as risk ratios (RR) for dichotomous outcomes and mean difference (MD) for continuous outcomes.

MAIN RESULTS

Two studies, including a total of 228 women with preterm labour and intact membranes, compared intravenous hydration with bed rest alone. Risk of preterm delivery, before 37 weeks (RR) 1.09; 95% confidence interval (CI) 0.71 to 1.68), before 34 weeks (RR 0.72; 95% CI 0.20 to 2.56) or before 32 weeks (RR 0.76; 95% CI 0.29 to 1.97), was similar between groups. Admission to neonatal intensive care unit occurred with similar frequency in both groups (RR 0.99; 95% CI 0.46 to 2.16). Cost of treatment was slightly higher (US$39) in the hydration group. This difference was not statistically significant and only includes hospital costs during a visit of less than 24 hours. No studies evaluated oral hydration.

AUTHORS' CONCLUSIONS

The data are too few to support the use of hydration as a specific treatment for women presenting with preterm labour. The two small studies available do not show any advantage of hydration compared with bed rest alone. Intravenous hydration does not seem to be beneficial, even during the period of evaluation soon after admission, in women with preterm labour. Women with evidence of dehydration may, however, benefit from the intervention.

Hydration for treatment of preterm labour

BACKGROUND

Hydration has been proposed as a treatment for women with preterm labour. Theoretically, hydration may reduce uterine contractility by increasing uterine blood flow and by decreasing pituitary secretion of antidiuretic hormone and oxytocin.

OBJECTIVES

To evaluate the effectiveness of intravenous or oral hydration to avoid preterm birth and its consequences in women with preterm labour.

SEARCH STRATEGY

The Cochrane Pregnancy and Childbirth Group trials register (January 2002), the Cochrane Controlled Trials register (The Cochrane Library, Issue 1, 2002) and bibliographies of relevant papers were searched.

SELECTION CRITERIA

Randomised controlled trials, including women with a viable pregnancy less than 37 completed weeks' gestation and presenting with preterm labour, comparing intravenous or oral hydration with no treatment. The intervention might or might not be associated with bed rest. Studies comparing tocolytic drugs with intravenous fluids used in the control group as a placebo were not included in this review.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed the reports, to determine if the study met the inclusion criteria and to evaluate the methodological quality. Data were extracted independently by two of the reviewers. The results were expressed as relative risks (RR) for dichotomous outcomes and weighted mean difference for continuous outcomes.

MAIN RESULTS

Two studies, including a total of 228 women with preterm labour and intact membranes, compared intravenous hydration with bed rest alone. Risk of preterm delivery, before 37 weeks (relative risk (RR): 1.09; 95% confidence interval (CI): 0.71-1.68), before 34 weeks (RR: 0.72; 95% CI: 0.20-2.56) or before 32 weeks (RR: 0.76; 95% CI: 0.29-1.97), was similar between groups. Admission to neonatal intensive care unit occurred with similar frequency in both groups (RR: 0.99; 95% CI: 0.46-2.16). Cost of treatment was slightly higher (US$39) in the hydration group. This difference was not statistically significant and only includes hospital costs during a visit of less than 24 hours. No studies evaluated oral hydration.

REVIEWER'S CONCLUSIONS

The data are too few to support the use of hydration as a specific treatment for women presenting with preterm labour. The two small studies available do not show any advantage of hydration compared to bed rest alone. Intravenous hydration does not seem to be beneficial, even during the period of evaluation soon after admission, in women with preterm labour. Women with evidence of dehydration may, however, benefit from the intervention.

Management options in women with preterm uterine contractions: a randomized clinical trial

OBJECTIVE

Our purpose was to evaluate three management strategies and to assess pregnancy outcomes in women with preterm uterine contractions.

STUDY DESIGN

Consenting women seen in our hospital triage area with preterm uterine contractions were randomly assigned to observation alone, intravenous hydration, or one dose of subcutaneous terbutaline sulfate (0.25 mg). Eligible women had a singleton gestation between 20 and 34 weeks, intact membranes, more than three contractions in 30 minutes, and a cervical dilation < or = 1 cm and effacement < 80%. Women who had progressive cervical change at < 34 weeks were treated with intravenous tocolysis. Women with recurrent preterm uterine activity remained in their assigned group during subsequent triage visits.

RESULTS

One hundred seventy-nine women were randomized: observation (56), hydration (62), and terbutaline (61). Women in these three groups were similar with respect to maternal age, race, parity, prior preterm births, gestational age at randomization, contraction frequency, and mean cervical dilatation. There were no intergroup differences in the mean days to delivery, the number of repeat triage visits, the incidence of preterm labor at < 34 weeks, or the frequency of preterm deliveries at < 34 weeks and < 37 weeks. Women assigned to terbutaline had contractions stopped and were discharged earlier (terbutaline 4.1 +/- 5.1 hours, observation 5.2 +/- 5.3 hours, hydration 6.0 +/- 5.7 hours; p = 0.006). No complications of therapy were observed.

CONCLUSIONS

The use of intravenous hydration in the management of preterm contractions was of no benefit. The use of one dose of subcutaneous terbutaline resulted in the shortest length of triage stay but did not affect pregnancy outcome.

Controlled trial of hydration and bed rest versus bed rest alone in the evaluation of preterm uterine contractions

Patients who are seen with uterine contractions but without documented change in cervical dilation or effacement are often treated with intravenous hydration before the initiation of intravenous tocolytic therapy. This is done with the intention of stopping uterine activity in patients with false preterm labor. A prospective randomized study was conducted to evaluate the effect of hydration on preterm uterine contractions in patients without proved preterm labor. A total of 28 patients were treated with bed rest and an intravenous bolus and subsequent continuous infusion of 5% dextrose in lactated Ringer's solution. A control group of 20 patients were treated with bed rest alone. Uterine activity and arrest of uterine contractions were compared between the two groups. Contractions stopped in 54% of the patients treated with hydration, whereas contractions stopped in 40% of the patients in the control group. This difference was not statistically significant. As a crossover study, those in the control group with contractions that continued after the initial observation period were subsequently treated with intravenous fluids. Only one patient in this group stopped contracting. Of all patients whose contractions with either therapy, 18% eventually were delivered of preterm infants. This included 20% of the hydration group and 14% of the control group. The use of hydration as a pretherapy indicator to differentiate true preterm labor from false preterm labor could not be supported by this study. In addition, patients whose contractions stopped with either hydration or bed rest are at increased risk of subsequent preterm delivery.