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Post-term Pregnancy and Induction of Labor
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10 IHS online resources
For additional resources please go to 11 Other Online Resources.
ACOG / IHS Postgraduate Reference Text
2003 ACOG / IHS Reference Text Online: POST-TERM PREGNANCY, pp 11-14 (pdf 190k)
UpToDate software
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Postterm pregnancy Norwitz, Errol
UpToDate software 10.3, 2003
Overview of fetal heart rate assessment Gillen-Goldstein, Jonathan
Young, Bruce
UpToDate software 10.3, 2003
Doppler ultrasound of the umbilical artery for fetal surveillance Maulik, Dev
UpToDate software 10.3, 2003
Fetal growth restriction: Diagnosis Divon, Michael, Ferber, Asaf
UpToDate software 10.3, 2003
Induction of labor: Indications, techniques, and complications Wing, Deborah
UpToDate software 10.3, 2003
Amnioinfusion: Indications and outcome Spong, Catherine, Ross, Michael
UpToDate software 10.3, 2003
Shoulder dystocia Rodis, John
UpToDate software 10.3, 2003
Cochrane Library
Crowley P. Interventions for preventing or improving the outcome of delivery at or beyond term (Cochrane Review). In: The Cochrane Library, Issue 1, 2003. Oxford: Update Software.
Implications for practice
In health systems in which reliable early pregnancy ultrasound is available at an acceptable cost, it should be performed routinely and the expected date of delivery should be revised, to avoid unnecessary induction of labour for a mistaken diagnosis of post-term pregnancy.
In health systems in which induction of labour is a safe and acceptable option, the question of induction of labour should be discussed with women after 41 weeks' gestation. They should be informed that about 500 inductions of labour may be necessary to prevent one perinatal death, and that there is no evidence that induction either increases or reduces the likelihood of delivery by Caesarean section. If the woman opts for induction of labour, the choice of method of induction should be based on evidence from randomized trials comparing the available methods. Women or obstetricians who opt for conservative management should be aware of the lack of evidence to support the effectiveness of any particular method of antenatal fetal surveillance.
The implications for practice in developing countries are likely to be different. Access to early pregnancy ultrasound is unlikely, the cost of induction of labour with vaginal prostaglandins is likely to be unacceptable and any reduction in perinatal mortality must be viewed in the context of overall perinatal and maternal risks locally.
Bricker L, Neilson JP. Routine ultrasound in late pregnancy (after 24 weeks gestation) (Cochrane Review).
In: The Cochrane Library, Issue 1, 2003. Oxford: Update Software.
Implications for practice
There is no evidence that routine ultrasound in late pregnancy improves perinatal outcome. However, its use does not appear to increase the rate of interventions, and hence the risk of iatrogenic morbidity. As a result of this review, it is not clear what aspects of late pregnancy ultrasound may be valuable in centres where it is undertaken. However, placental grading appears to be useful, and perhaps should be considered in late pregnancy ultrasound, whether routine or selective.
Tan KH, Smyth R. Fetal vibroacoustic stimulation for facilitation of tests of fetal wellbeing (Cochrane Review).
In: The Cochrane Library, Issue 1, 2003. Oxford: Update Software.
Implications for practice
By reducing the number of non-reactive cardiotocography secondary to fetal sleep states and reducing the testing time, fetal vibroacoustic stimulation may help perinatal resources to be better utilized. By evoking fetal movements, fetal vibroacoustic stimulation may be useful in ultrasound examination and evaluation of fetal wellbeing.
However, due to the void in the literature of randomised controlled trials relating to important outcomes such as fetal hearing impairment, impairment of neurological development, maternal satisfaction and maternal anxiety and perinatal mortality, there is still currently insufficient evidence within randomised controlled trials upon which to base a firm recommendation regarding the routine use of fetal vibroacoustic stimulation.
Hofmeyr GJ , Gulmezoglu AM. Vaginal misoprostol for cervical ripening and induction of labour (Cochrane Review).
In: The Cochrane Library, Issue 1, 2003. Oxford: Update Software.
Implications for practice
In dosages of 25 micrograms three hourly or more, vaginal misoprostol is more effective than conventional methods of cervical ripening and labour induction. However, uterine hyperstimulation with fetal heart rate changes are increased. Although no differences in perinatal outcome were shown, the studies were not sufficiently large to exclude the possibility of uncommon serious adverse effects. The trend to an increase in meconium stained liquor also requires further investigation. Anecdotal reports of uterine rupture following labour induction with misoprostol are cause for concern.
The limited information on lower dosage regimens suggests that they may be as effective as other prostaglandins, without increased uterine hyperstimulation. Thus, though misoprostol shows promise as a highly effective, inexpensive and convenient agent for labour induction, it cannot be generally recommended for routine use at this stage. It is also not registered for such use in many countries.
As the relative weighting of demonstrated benefits (including cost) and potential risks will vary from one setting to another, it is important for professional or governmental bodies to agree guidelines on the use of misoprostol, taking into account the best available evidence as well as local circumstances.
Kelly AJ, Kavanagh J, Thomas J. Vaginal prostaglandin (PGE2 and PGF2a) for induction of labour at term (Cochrane Review).
In: The Cochrane Library, Issue 1, 2003. Oxford: Update Software.
Implications for practice
The use of vaginal PGE2 appears to be an effective induction agent. Compared with no treatment or placebo the likelihood of vaginal birth within 24 hours is increased. There is a reduction in the use of oxytocin augmentation and no effect on the rate of caesarean section. The use of vaginal PGE2 tablets as an alternative to other vaginal PGE2 formulations is recommended.
Howarth GR, Botha DJ. Amniotomy plus intravenous oxytocin for induction of labour (Cochrane Review).
In: The Cochrane Library, Issue 1, 2003. Oxford: Update Software.
Implications for practice
Although amniotomy and intravenous oxytocin have been used widely in obstetric practice, the available literature does not clearly support or refute the value of using the combination instead of the separate methods individually. 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. Cognizance however must be taken of the possibility of increased perinatal transmission of HIV following amniotomy particularly in areas where the prevalence of HIV may be high and due to limited resources or other reasons HIV status of the woman is unknown.
Alfirevic Z, Neilson JP. Biophysical profile for fetal assessment in high risk pregnancies (Cochrane Review).
In: The Cochrane Library, Issue 1, 2003. Oxford: Update Software.
Implications for practice
The data are insufficient to reach any definite conclusion about the benefit or otherwise of the biophysical profile as a test of fetal well-being.
Neilson JP, Alfirevic Z. Doppler ultrasound for fetal assessment in high risk pregnancies (Cochrane Review).
In: The Cochrane Library, Issue 1, 2003. Oxford: Update Software.
Implications for practice
Doppler ultrasound is a relatively new technique to be applied to the study of feto-placental and/or uteroplacental circulatory dynamics. Although it has been evaluated more rigorously than any other biophysical test of fetal growth or wellbeing, the numbers of women included in the different trials fall somewhat short of the power calculations which preceded a recent systematic review of this subject. The numbers have decreased with exclusion of the Pearce trial data (as has the confidence with which one can ascribe the reduced perinatal mortality rate to the use of Doppler ultrasound). Readers will either regard these findings as sufficiently sound to justify the use of Doppler ultrasound in high risk pregnancies (especially those complicated by hypertension or presumed fetal growth restriction), or see the findings as sufficiently promising to justify a larger, and hopefully definitive, trial.
Boulvain M, Stan C, Irion O. Membrane sweeping for induction of labour (Cochrane Review).
In: The Cochrane Library, Issue 1, 2003. Oxford: Update Software.
Implications for practice
The available evidence suggests that sweeping the membranes promotes the onset of labour. For women thought to require induction of labour, a reduction in the use of more formal methods of induction could be expected. For women near the term in an uncomplicated pregnancy there seems to be little justification for performing routine sweeping of membranes. Sweeping of the membranes is probably safe, provided that the intervention is avoided in pregnancies complicated by placenta praevia or when contraindication for labour and/or vaginal delivery are present. There is no evidence that sweeping the membranes increases the risk of maternal and neonatal infection, or of premature rupture of the membranes. However, women's discomfort during the procedure and other side effects must be balanced with the expected benefits before submitting women to sweeping of the membranes.
Hofmeyr GJ. Amnioinfusion for umbilical cord compression in labour (Cochrane Review).
In: The Cochrane Library, Issue 1, 2003. Oxford: Update Software.
Implications for practice
Convincing evidence is available from these trials that amnioinfusion for potential or suspected umbilical cord compression reduces the occurrence of variable fetal heart rate decelerations. No important effect on longer term neonatal outcome has been detected. Of considerable importance is the large reduction in Caesarean sections, which is accounted for by a reduction in operations performed for 'fetal distress'. As no mention is made of fetal scalp blood sampling in any of the studies, this diagnosis may have been based on fetal heart rate patterns alone.
Extrapolation of the results as a guide to clinical practice should therefore be limited to clinical situations in which Caesarean sections are commonly performed for abnormal fetal heart rate patterns alone. Under these circumstances the use of amnioinfusion for potential or suspected umbilical cord compression may be of considerable benefit to the mother, though the methodological limitations of the trials reviewed here need to be kept in mind. Preferably, however, scalp sampling should be used to assess the significance of fetal heart rate abnormalities. Under such circumstances the effectiveness of amnioinfusion is unknown.
The trials reviewed are too small to address the possibility of rare but serious maternal side-effects of amnioinfusion. Several case reports have been published of cardiac failure or amniotic fluid embolism following amnioinfusion, though a causal relationship has not been established. The benefits shown in the trials reviewed need to be weighed against the theoretical small risk of serious maternal complications. Far larger trials are needed to address the risk-benefit ratio of amnioinfusion conclusively.
Trials in this review include the use of amnioinfusion both prophylactically for situations such as oligohydramnios, or therapeutically for fetal heart rate decelerations. The limited evidence available suggests that there is no advantage to using amnioinfusion prophylactically as opposed to therapeutically.
The trials of transabdominal amnioinfusion, though small, suggest that similar results are achieved as with transcervical amnioinfusion. The risk of transabdominal insertion of a needle into the amniotic cavity needs to be weighed against several theoretical advantages of the transabdominal route in women with intact membranes: the membranes do not need to be ruptured to perform amnioinfusion; there is no ongoing leakage of amniotic fluid, so that a single infusion is likely to be effective for several hours; and the discomfort, inconvenience and possible risks of an indwelling intrauterine catheter are avoided.
The single trial of amnioinfusion to reduce infection in women with ruptured membranes for longer than 6 hours has shown encouraging results, but is too small to be used as a basis for changes in clinical practice.
Hofmeyr GJ. Amnioinfusion for meconium-stained liquor in labour (Cochrane Review).
In: The Cochrane Library, Issue 1, 2003. Oxford: Update Software.
Implications for practice
Units with standard peripartum surveillance:
The reduction in the incidence of the diagnosis of meconium aspiration syndrome after amnioinfusion in these studies is of significance and may possibly be due to a reduction in fetal distress related to oligohydramnios (see Cochrane review 'Amnioinfusion in intrapartum umbilical cord compression (potential, or diagnosed by electronic fetal heart rate monitoring)' (Hofmeyr 1997a)
).
Whether amnioinfusion influences the outcome in pregnancies with meconium-stained liquor unrelated to the correction of oligohydramnios has yet to be determined. At the least, the evidence shows a benefit of the use of amnioinfusion in pregnancies complicated by meconium-stained amniotic fluid together with oligohydramnios.
The trials reviewed are too small to address the possibility of rare but serious maternal side-effects of amnioinfusion. Several case reports have been published of cardiac failure or amniotic fluid embolism following amnioinfusion, though a causal relationship has not been established. The benefits shown in the trials reviewed need to be weighed against the theoretical small risk of serious maternal complications. Larger trials, with fewer exclusions, are needed to address the risk-benefit ratio of amnioinfusion conclusively.
Units with limited peripartum surveillance:
The study of Mahomed 1998 has shown a striking improvement in perinatal outcome with a simplified technique of amnioinfusion. The use of amnioinfusion should be considered for women with meconium stained liquor in units with limited facilities for peripartum surveillance and high rates of meconium aspiration syndrome.
The diagnosis of meconium stained liquor may be limited by a policy of maintaining intact membranes during labour in areas with a high prevalence of HIV infection. Once meconium stained liquor is diagnosed, whether amnioinfusion would increase the risk of vertical HIV transmission to the fetus because of placement of the intrauterine catheter, or reduce the risk by irrigation of the genital tract and dilution of maternal fluids, is not known.
Hofmeyr GJ. Prophylactic versus therapeutic amnioinfusion for oligohydramnios in labour (Cochrane Review).
In: The Cochrane Library, Issue 1, 2003. Oxford: Update Software.
Implications for practice
The findings of the two studies reviewed do not support the use of amnioinfusion prophylactically for oligohydramnios alone, rather than therapeutically only when fetal heart rate decelerations (or thick meconium-staining of the amniotic fluid) occur. Given that amnioinfusion is an invasive and uncomfortable procedure, and the uncertainty concerning the possibility of rare maternal complications prophylactic amnioinfusion for oligohydramnios alone does not appear to be justified in routine clinical practice.
Hofmeyr GJ, Kulier R. Operative versus conservative management for 'fetal distress' in labour (Cochrane Review).
In: The Cochrane Library, Issue 1, 2003. Oxford: Update Software.
Implications for practice
The changes in obstetric practice and methods of fetal evaluation since the trial of Walker 1959 make it difficult to relate the results to contemporary obstetric practice. For those working in situations without modern obstetric facilities, it is useful to note that in this situation the policy of operative delivery in the event of meconium-stained liquor or fetal heart rate changes causes a considerable increase in operative deliveries, and has not been shown to reduce perinatal mortality.
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