Amnioinfusion for potential or suspected umbilical cord compression in labour
Transcervical amnioinfusion reduces the frequency of variable fetal heart rate decelerations and reduces the risk of caesarean section. However, the benefits, if any, of transabdominal amnioinfusion must be weighed against potential harm from needle insertion.
RHL Commentary by Boulvain M
1. EVIDENCE SUMMARY
This review evaluates the effect of transcervical amnioinfusion performed for potential or suspected umbilical cord compression. Suspicion of cord compression was usually based on oligohydramnios detected by ultrasound and/or fetal heart rate monitoring showing repetitive variable decelerations. The review of all available controlled trials shows that amnioinfusion reduces the frequency of variable fetal heart rate decelerations and reduces the risk of caesarean section, especially caesarean section for suspected fetal distress. The author stresses that the reports included in the review do not mention the use of scalp pH to confirm fetal distress suspected by the presence of fetal heart rate abnormalities. It is unclear whether amnioinfusion will be associated with a similar reduction in the caesarean section rate when used in a context where the diagnosis of fetal distress is confirmed by scalp blood pH.
The review of the trials evaluating transabdominal amnioinfusion concludes that the benefits, if any, of this intervention must be weighed against potential harm from needle insertion. Amnioinfusion after rupture of membranes for more than six hours was evaluated in one small trial that suggested a reduction of the risk of puerperal infection. Both interventions are not as yet adequately evaluated, and thus this commentary will not include a discussion on these aspects.
The methodology used for this systematic review is appropriate. Criteria for inclusion and exclusion of controlled trials are well described. Main outcomes were pre-specified, and effects on intermediate outcomes (e.g. fetal heart rate decelerations, Apgar score) are given appropriate weight in the conclusions.
2. RELEVANCE TO UNDER-RESOURCED SETTINGS
2.1. Magnitude of the problem
Perinatal mortality is high in under-resourced settings. Intrapartum mortality and morbidity is of particular concern in such settings. Fetal distress caused by cord compression could be one of the causes leading to intrapartum death. The frequency of fetal distress, which could potentially benefit from amnioinfusion, however, is largely unknown.
2.2. Feasibility of the intervention
Detection of oligohydramnios or of variable decelerations of the fetal heart rate, which leads to the suspicion of compression of umbilical cord, might not be feasible in under-resourced settings.
Catheters designed to perform amnioinfusion are expensive, but amnioinfusion can be performed with less expensive instruments such as neonatal suction catheters, which are widely available. The technique is simple, but requires some training before it can be performed optimally. In considering the implementation of this intervention, the availability and cost of sterile fluids must also be taken into account.
2.3. Applicability of the results of the Cochrane Review
The studies reviewed were conducted using electronic fetal monitoring, easy access to caesarean section and immediate paediatric facilities. From a maternal perspective the major advantage is a decrease in caesarean sections. In units where fetal monitoring is by intermittent auscultation and the rate of caesarean section lower, the benefit from amnioinfusion may not be as high. Conversely, it is possible that in units where immediate neonatal care is not available, the effects on neonatal outcomes may be more important than shown in the systematic review.
2.4. Implementation of the intervention
Implementing this intervention using less expensive catheters is possible. Amnioinfusion for variable decelerations was assessed in centres performing caesarean section for fetal distress suspected on the basis of fetal heart rate abnormalities, without confirmation by scalp blood pH. It might be possible that the benefit of amnioinfusion is confined to reducing variable decelerations, a rather unspecific sign of fetal distress. However, despite the fact that implementing scalp blood pH would be an advantage, the intervention is beneficial for the mother if it reduces the likelihood of caesarean section in that context.
The benefits and harms of amnioinfusion must be evaluated in hospitals where fetal well-being is monitored by intermittent auscultation. More research is also needed to evaluate the effect of amnioinfusion for cord compression, suspected on the basis of fetal heart rate decelerations, on caesarean section, in a context where scalp blood pH is performed.
Sources of support: University of Geneva, Geneva, Switzerland
Acknowledgement: This commentary was previously prepared by Prof. Graham Howarth.
This document should be cited as: Boulvain M. Amnioinfusion for potential or suspected umbilical cord compression in labour: RHL commentary (last revised: 24 June 2002). The WHO Reproductive Health Library; Geneva: World Health Organization.