Intrauterine pressures in labours induced by amniotomy and oxytocin or vaginal prostaglandin gel compared with spontaneous labour

Induction of labour at the start of the new millennium

Around 20% of all deliveries are preceded by labour induction, a proportion that has not varied dramatically over recent years. Fetal death was the only indication for labour induction centuries ago, while this is now a very rare indication, with prolonged pregnancy and maternal hypertensive disorders being the major indications for the last 50–60 years. Techniques for inducing labour have also changed from dietary delicacies and verbal threats giving way to physical stimulation mainly achieved by cervical stretching and amniotomy and more recently to sophisticated pharmacological manipulation using oxytocin and prostaglandins, based on our expanding knowledge of the physiological processes involved in spontaneous parturition. Relaxin, antiprogestins, nitric oxide as well as complementary medicines have also been explored in recent years. Successful induction is, however, still not guaranteed and there has been increasing emphasis during the past decade on exploring strategies for identifying the probability of success. Measurement of fetal fibronectin in cervical mucus, maternal serum nitrite/nitrate concentrations, ultrasound delineation of cervical form and electrical impedance measurements across the cervix are all being investigated. Safety, success, and patient satisfaction continue to be the major objectives with economic evaluations now becoming a significant factor in the search for the ideal induction method.

Prise en charge obstétricale des grossesses prolongées au-delà de 41 semaines d’aménorrhée avec un score de Bishop défavorable

OBJECTIVE

Our purpose was to determine the optimal management of pregnancies beyond 41 week's gestation with a cervix unfavorable for induction.

MATERIAL AND METHOD

All uncomplicated pregnancies that reached 41 weeks'gestation with a Bishop score of< or =4, were randomly assigned to one of two groups

RESULTS

The duration of labor was shorter in the group "prépidil" compared with the control group (P=0.002). Identification of an unfavorable cervix at 41 weeks was unlikely to change by 42 weeks and cervical ripening was required in 40% cases. There was no significant difference in caesarean section rates. Rates of admission into the neonatal unit and fetal outcomes were similar in the two groups.

CONCLUSION

Cervical ripening with prostaglandin gel at 41 week's gestation for uncomplicated singleton pregnancies is safe and should be advocated.

Amniotomy plus intravenous oxytocin for induction of labour

BACKGROUND

Induction of labour is a common obstetric intervention. Amniotomy alone for induction of labour is reviewed separately and oxytocin alone for induction of labour is being prepared for inclusion in The Cochrane Library. This review will address the use of the combination of these two methods for induction of labour in the third trimester. This is one of a series of reviews of methods of cervical ripening and labour induction using standardised methodology.

OBJECTIVES

To determine, from the best available evidence, the efficacy and safety of amniotomy and intravenous oxytocin for third trimester induction of labour.

SEARCH STRATEGY

The Cochrane Pregnancy and Childbirth Group Trials Register, the Cochrane Controlled Trials Register and reference lists of articles were searched. Date of last search: May 2001.

SELECTION CRITERIA

The criteria for inclusion included the following: (1) clinical trials comparing amniotomy plus intravenous oxytocin used for third trimester cervical ripening or labour induction with placebo/no treatment or other methods listed above it on a predefined list of labour induction methods; (2) random allocation to the treatment or control group; (3) adequate allocation concealment; (4) violations of allocated management not sufficient to materially affect conclusions; (5) clinically meaningful outcome measures reported; (6) data available for analysis according to the random allocation; (7) missing data insufficient to materially affect the conclusions.

DATA COLLECTION AND ANALYSIS

Trial quality assessment and data extraction were done by both reviewers. A strategy was developed to deal with the large volume and complexity of trial data relating to labour induction. This involved a two-stage method of data extraction. The initial data extraction was done centrally, and incorporated into a series of primary reviews arranged by methods of induction of labour, following a standardised methodology. The data is to be extracted from the primary reviews into a series of secondary reviews, arranged by category of woman.

MAIN RESULTS

Seventeen trials involving 2566 women were included. Amniotomy and intravenous oxytocin were found to result in fewer women being undelivered vaginally at 24 hours than amniotomy alone (relative risk (RR) 0.03, 95% confidence intervals (CI) 0.001-0.49). This finding was based on the results of a single study of 100 women. As regards secondary results amniotomy and intravenous oxytocin resulted in significantly fewer instrumental vaginal deliveries than placebo (RR 0.18, CI 0.05-0.58). Amniotomy and intravenous oxytocin resulted in more postpartum haemorrhage than vaginal prostaglandins (RR 5.5, CI 1.26-24.07). Significantly more women were also dissatisfied with amniotomy and intravenous oxytocin when compared with vaginal prostaglandins, RR 53, CI 3.32-846.51.

REVIEWER'S CONCLUSIONS

Data on the effectiveness and safety of amniotomy and intravenous oxytocin are lacking. No recommendations for clinical practice can be made on the basis of this review. Amniotomy and intravenous oxytocin is a combination of two methods of induction of labour and both methods are utilised in clinical practice. If their use is to be continued it is important to compare the effectiveness and safety of these methods, and to define under which clinical circumstances one may be preferable to another.

Randomized comparison of the effects of endocervical and vaginal prostaglandin E2 gel in women with various degrees of cervical ripeness. Dutch Collaborative Prostaglandin Trialists' Group

OBJECTIVE

The trail was conducted to obtain an unbiased comparison of the relative merits of endocervical and vaginal prostaglandin E2 gel in a weighted case mix of parous and nulliparous women with favorable and unfavorable cervical features.

STUDY DESIGN

Multicenter randomized trial with 285 participants, (three exclusions) was performed with sealed envelopes stratified for parity and Bishop score.

RESULTS

Outcomes of labor and delivery were clearly related to the cervical score at trial entry, especially in nulliparous women. Endocervical prostaglandin E2 had a more marked effect on cervical ripeness than did vaginal prostaglandin E2, but this did not result in any differences in more substantive outcomes. Frequencies of delivery within 12 (50%) and 24 hours (77.7%), cesarean section (7.3%), instrumental vaginal delivery (11.7%), and poor infant outcomes were similar with both preparations.

CONCLUSION

Because differences in effectiveness between endocervical and vaginal prostaglandin E2 in triacetin gel are marginal, preferences of women and clinicians can determine the choice between them.

Oxytocics in developing countries

OBJECTIVES

A prospective multicenter study of obstetric practices was conducted in three developing countries (Benin, Congo and Senegal) to analyze oxytocic use during labor. One of the objectives was to assess the possible negative effects of the treatment regimens instituted during the labor monitoring phase.

METHODS

Four health districts participated in the study. All women who gave birth in one of the participating health facilities over a 6-month period in Benin and Congo, and over a 3-month period in Senegal, were recruited. The number of deliveries studied in each district varied from 457 to 1048. For each case a partogram was used to assess the progress of labor and the onset of dysfunctional labor. Information was collected on the risk factors for dysfunctional labor, stillbirths and resuscitation of the neonate.

RESULTS

Each of the four collaborating centers used oxytocics preferentially to treat dysfunctional labor, but even in normal labor (i.e. with a normal partogram) oxytocics were used in 4.4-21.5% of cases. In normal labor the incidence of neonatal resuscitation was higher in cases with than in those without oxytocic use: the relative risks (R.R.) varied from 1.9 to 5.6; the odds ratios varied from 2.4 to 7.0, and both were statistically significant in the four settings. In addition the stillbirth rate was always higher, though not significantly, when oxytocics were used in normal labor (R.R. 1.2-2.2). When the data of the four centers were pooled, the global relative risk for stillbirths was 1.9, and the 95% confidence interval was 1.1-3.4. Logistic regression analysis was carried out for five confounding factors (primiparity, a previous complicated delivery, presence of meconium, ruptured membranes and educational level) to adjust the odds ratio for the risk of neonatal resuscitation when oxytocics were used in normal labor. Except in the case of Abomey in Benin, where the variable 'presence of meconium' decreased the odds ratio from 6.4 to 3.4, the adjusted odds ratios remained similar to their non-adjusted values. In cases of non-dysfunctional labor, nurses and midwives used oxytocics more often than lesser trained health personnel (R.R. 4.0 [3.2-5.1]).

CONCLUSION

Our results show that an obstetric treatment which is safe when used in certain well-defined indications, may have significant negative effects when used in situations where the same technical quality of care cannot be guaranteed.

Intrauterine pressure: comparison of extra vs intra amniotic methods using a transducer tipped catheter

Fourteen women admitted in early labor, with intact membranes, were studied. In each woman, two catheters were inserted transcervically; one catheter was inserted into the extraamniotic space before rupture of membranes, and the second catheter was inserted, after artificial rupture of membranes into the intraamniotic cavity. The contraction to contraction difference in active pressure (pressure above the baseline) recorded by the two catheters, as well as the cumulative total active pressure generated (calculated by adding the active pressure of all contractions) throughout labor by the two catheters were compared. Of the 606 contractions analysed, 43.2% showed pressure difference of 0-5 mmHg between the intra amniotic and extraamniotic catheter; 21.3% showed 6-10 mmHg difference, 12.2% showed a difference of 11-15 mmHg, and 23.3% showed a difference greater than 15 mmHg. When total active pressure generated by each catheter for individual patients was calculated, the percentage difference varied from 2.3% to 53.7%. Intrauterine pressure measurements in labour using transducer-tipped catheters inserted in the extraamniotic space may not provide comparable information to a similar catheter inserted intraamniotically when membranes are ruptured.

Cervical contractions: the response of the cervix to oxytocic stimulation in the latent phase of labour

OBJECTIVE

To assess the cervical response to myometrial activity in early labour.

DESIGN

Prospective observational study.

SUBJECTS

Women requiring oxytocin stimulation in induced and spontaneous labours.

SETTING

A teaching hospital in Birmingham.

MAIN OUTCOME MEASURES

Simultaneous comparison of the cervical response to myometrial contractions was made on a cycle by cycle basis to deduce the properties of the cervix in early labour.

RESULTS

Sixty-seven patients have been monitored, of whom 63 had satisfactory cervimetry data. Thirty (47.6%) women exhibited cervical contractions in response to myometrial activity. This response was only observed at dilatations up to 4 cm. The change in behaviour coincides with the transition from latent to active phases of dilatation. The length of the latent phase of labour was significantly longer in those women who exhibited cervical contractions (P < 0.001), although the active phase was similar in the two groups (P > 0.1). The group without cervical contractions exhibited a greater degree of effacement (P < 0.05) and tended to have more dilated cervices (P < 0.01) than those who showed cervical contractions.

CONCLUSIONS

It is possible for the cervix to contract in early labour. This response may be the result of incomplete preparation of the cervix for the process of dilatation, and is seen during what is recognised as the latent phase in those women in whom the cervix is unaffected and undilated. These properties of the cervix may explain the poor results obtained from oxytocin stimulation of labour in the latent phase.

Standards in fetal monitoring--practical requirements for uterine activity measurement and recording

External monitoring of uterine contractility in human labour can record contraction frequency accurately, but cannot determine true intra-uterine pressure reliably. It is therefore suitable for use in spontaneous labour where there is a need for a marker of contractions to aid in continuous fetal heart rate pattern interpretation. Intra-uterine pressure measurement can provide quantitative information more reliably over intervals of 10-60 minutes. Although active pressure values for individual contractions can vary by up to 50% when measured simultaneously by two or more intra-uterine catheters/transducers, this variation is not systematic and cumulative measures vary by less than 5%. The measurement of baseline tone is affected by variables not related to uterine activity and should therefore be excluded when quantitative measures are made.