Follow-up of hydration and sedation in the pretherapy of premature labor

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.

Prevention of preterm birth

For an infant without lethal congenital malformations there is no risk greater than to be born too early. In addition, preterm birth with its many consequences may compromise the life of the whole family. Thus, prevention of preterm birth is one of the greatest challenges in obstetrics. However, this has proven to be difficult. This difficulty is in part due to the fact that, although we know a large number of clinical factors which are know a large number of clinical factors which are associated with preterm birth, the final mechanisms triggering the onset of preterm contractions or premature rupture of the fetal membranes (PROM) have remained largely unclear. We review the prevention of preterm birth in the light of the newest data; an interested reader is also referred to other recent overviews on the same topic.

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.

Evaluating the risk of preterm delivery: a comparison of fetal fibronectin and transvaginal ultrasonographic measurement of cervical length

OBJECTIVE

Our purpose was to compare the predictive values for preterm delivery of fetal fibronectin and cervical length measured by transvaginal ultrasonography and to determine whether performing both tests improves their separate predictive values.

STUDY DESIGN

This prospective blinded study performed both tests on 76 patients hospitalized with signs of premature labor between 24 and 34 weeks of gestation. The outcome measure was delivery before 37 weeks' gestation.

RESULTS

The rate of preterm bith was 26.3% (20/76). The predictive values of fetal fibronectin and of a cervical length of < or = 26 mm, considered separately, were approximately equal, and the negative predictive value of each was excellent (86.6% and 89.1%, respectively). This value improved slightly when positive fetal fibronectin, a cervical length < or = 26 mm, or both defined abnormality (negative predictive value 94.4%). The positive predictive values, although less helpful, were still useful (45.2% and 50.0%, respectively). Combining both indicators did not noticeably improve the positive predictive value (52.4%). The risk of preterm delivery for a patient with a positive fetal fibronectin level and a short cervix was high (odds ratio 13.9, 95% confidence interval 3.7 to 52.2).

CONCLUSION

Fetal fibronectin and cervical length are approximately equivalent in their ability to distinguish between patients at high and low risk for preterm delivery. For physicians equipped to perform transvaginal ultrasonography, however, the additional information about the fibronectin level provides only slight benefits.

Haemodynamic consequences and uterine contractions following 0.5 or 1.0 litre crystalloid infusion before obstetric epidural analgesia

PURPOSE

The efficacy of infusion of 0.5 L and 1.0 L Ringer's lactate (LR) to prevent hypotension during induction of obstetric analgesia was studied. The effect of the different fluid boluses on fetal heart rate (FHR) and frequency of uterine contractions were also determined.

METHODS

Ninety-two ASA 1-2 parturients were randomized to receive 0.5 L (Group 1) and 1.0 L (Group 2) LR immediately before incremental epidural injections with lidocaine to achieve T10 sensory block. Systolic blood pressure (SBP) was measured with an automated BP cuff every two minutes for 30 min after infusion of fluid bolus. Fetal heart rate monitoring and tocometry were used continuously. The number of uterine contractions were recorded 30 min before and 60 min after i.v. bolus.

RESULTS

The SBP decreased in both groups, but there was no difference between groups in mean SBP or maternal heart rate. The incidence of hypotension (SBP < 90 mmHg or decrease of 20%) was 4% in both groups. The FHR record of a patient in Group 1 showed a single late deceleration, and a decrease in beat-to-beat variability occurred in one patient in Group 2. A decrease in the frequency of uterine contractions of two or more contractions per 30 min was noted more frequently in Group 2 (P < 0.05). The duration of iv bolus was longer in Group 2 than Group 1 (18.8 +/- 4.3 min vs 12.3 +/- 4.5 min, P < 0.01).

CONCLUSION

Administration of 1.0 L LR i.v. does not provide added protection against maternal hypotension, and is associated with delay in providing pain relief and a risk of decreasing uterine contraction frequency.

Oncofetal fibronectin in patients with false labor as a predictor of preterm delivery

OBJECTIVE

Our objective was to determine whether fetal fibronectin is a discriminator for preterm labor and early delivery in women who have intact membranes and uterine activity.

STUDY DESIGN

In our prospective study 28 women between 24 and 34 weeks' gestation with regular, persistent uterine contractions (> 10/hr) and intact membranes were assessed for presence of fetal fibronectin. A Dacron swab was applied to the external os for 10 seconds. The cervix was < or = 1 cm, and all patients were diagnosed as having false labor. The assay was performed by using monoclonal antibody FDC-6 to bind fetal fibronectin.

RESULTS

Of the 28 patients with false labor, 14 had a positive fetal fibronectin, and all had preterm labor (specificity and positive predictive value 100%). Of these, nine delivered preterm, yielding a specificity and positive predictive value of 72% and 64%, respectively. Among the 14 women with a negative fetal fibronectin, only four developed preterm labor (sensitivity 78%, negative predictive value 71%). One patient delivered preterm at 34 weeks (sensitivity 90% and negative predictive value 93%).

CONCLUSIONS

A positive fetal fibronectin in women who have false labor indicates a significant risk for preterm labor and early delivery. A negative fetal fibronectin is a reassuring sign.

Acute intrauterine hypoxia increases amniotic fluid prostaglandin F metabolites in the pregnant sheep

OBJECTIVE

Amniotic fluid infection promotes cytokine release, prostaglandin production, and premature labor. In several tissues local hypoxia also activates the secretion of cytokines. Many patients initially seen in premature labor carry small-for-gestational-age fetuses, a condition associated with intrauterine hypoxia. The purpose of our study was to determine whether a reduction in placental blood flow and subsequent acute hypoxia affects prostaglandin secretion by the placenta.

STUDY DESIGN

We chronically catheterized six pregnant sheep at 120 days of gestation. We placed catheters in the maternal and fetal femoral arteries and in the amniotic fluid cavity. A flow probe and snare were placed around the common uterine artery.

RESULTS

A 30-minute uterine circulation occlusion of 30% of its control value produced an increase in prostaglandin F metabolite from 790 +/- 157 to 944 +/- 184 pg/ml within 10 minutes (p < 0.01). Additional uterine blood flow reduction to 60% of control increased the amniotic fluid prostaglandin F metabolites concentration to 894 +/- 202 (p < 0.05, analysis of variance). No increase in mean intrauterine pressure was detected (p > 0.1).

CONCLUSIONS

We speculate that the prostaglandin increase in amniotic fluid in response to intrauterine hypoxia could eventually lead to premature labor. Whether the increase in prostaglandins is mediated by changes in cytokines is unknown at the present time.

The predictive value of fetal breathing movement and Bishop score in the diagnosis of "true" preterm labor

In 70 patients who were between 32 and 36 weeks' gestation and who complained of painful uterine contractions, real-time ultrasonography was performed to establish the presence or absence of fetal breathing. Ten of the 14 women in whom no fetal breathing movement could be detected were delivered of infants within 48 hours, whereas the pregnancies continued for a week or longer in 52 of the 56 patients in whom fetal breathing was present. There was a good correlation between Bishop score and pregnancy outcome. Of the 48 patients with "unfavorable" cervix (Bishop score less than or equal to 3), 45 were delivered of infants after 1 week or more, whereas of 22 patients with a Bishop score of 4 to 6, nine were delivered of infants within 48 hours and ten pregnancies continued for 1 week or more.

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.