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Perspective on meconium staining of the amniotic fluid
  1. Sam J Oddie
  1. Correspondence to Dr Sam J Oddie, Department of Neonatology, Bradford Royal Infirmary, Bradford, UK; samoddie{at}bradfordhospitals.nhs.uk

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Perspective on the paper by van Ierland et al (see page 69)

Meconium staining of the amniotic fluid (MSAF) commonly complicates delivery at or around term. Thick meconium is more likely than thin to cause associated lung disease and more asphyxiated infants have long been known to be at higher risk of lung disease.1

In addition, the incidence meconium aspiration syndrome (MAS) varies geographically,2 by gender and by ethnicity as well as by place of delivery (with planned home deliveries reported as being at more than twice the risk).3 Optimal management of the common condition of MSAF thus has the potential to result in marked improvements in worldwide health outcomes. Furthermore, there are suggestions of a temporal change in the rates of MAS, with a large cohort study of MAS showing a reduction in incidence over recent years, albeit only in those infants born at or after 41 weeks of gestation.3 Those and other authors have suggested that obstetric interventions were important in moderating the risk of MAS.3 4

Globally, neonatology’s approach to the management of MSAF has changed, most signally in response to the classic papers of Wiswell and colleagues1 and Vain et al.5 They showed that interventions after the delivery of the infant’s head do little to affect the incidence of MAS, despite the fact that a third of apparently vigorous infants born through MSAF have meconium in the trachea at delivery.1 Tracheal suction for “depressed” infants with meconium in the trachea remains recommended but unproved.6 It is reasonable to doubt its effectiveness in preventing MAS as it is known that fetuses may aspirate meconium deep into the lung in terminal agonal gasping.7 However, the use of tracheal suction as a treatment for meconium airway obstruction remains well accepted.8

What of the 90% of babies delivered through MSAF who neither develop MAS nor any other breathing difficulty?5 How should such babies be identified and managed? Ierland and colleagues9 have gone some way to answering this question, reviewing their experience of which infants develop MAS after delivering through MSAF. For infants felt to be entirely well early in life—here defined as having a 5-minute APGAR score of 9 or 10—the risk of MAS appears very low indeed. One baby, from 298 born through MSAF who initially appeared well, went on to develop MAS (measured risk 0.3%; 95% CI 0.03% to 1.8%), and this baby was symptomatic by 15 minutes of age. Can we therefore be confident that our use of the Apgar score will allow us safely to “discharge vigorous newborns”?

The authors used the Apgar score as a metric for the successful transition of the newborn. In their practice, scores were attributed by either the obstetrician or the paediatrician. In their paper on interobserver variability of the 5-minute Apgar score, O’Donnell and colleagues10 reasonably speculate that the Apgar “score is frequently assigned when one or more elements are not formally assessed”. It is not known if this could apply to obstetricians and neonatologists in The Netherlands or elsewhere. If it did, at this high Apgar threshold, variability in the awarding of a score of either 8 or 9 would make a big difference to the implied management. Furthermore, using the Apgar score alone to predict progression to MAS has a chequered history—in one large population-based study a third of babies who eventually died from MAS were judged as neither needing intubation nor having an Apgar score or less than 7 at 5 minutes.3

We could put reservations about the Apgar score to one side, and accept that those babies given an Apgar score of 9 or 10 at 5 minutes are the same as those who are well. Perhaps then we can simply discharge those infants who are well at 5 minutes of age, or indeed review them when a little older, and discharge them then? Might not the emerging literature on screening for neonatal illness using universal or selective oxygen saturation screening be a relevant area for study here? Its hard to see how a low peripheral oxygen saturation could reasonably be seen to delay discharge inappropriately.11 12

Perhaps our decisions about discharging the apparently well baby can be informed by national guidance? The American Academy of Pediatrics has issued careful and baby focussed guidance on who is suitable for early hospital discharge for use in an environment where hospital delivery is the norm.13 It makes no specific mention of MSAF, but perhaps such infants are seen as high risk and thus unsuitable for early hospital discharge?

The UK has its National Institute for Health and Clinical Excellence (NICE), who are at times less forensic in their approach.14 In issuing guidance for the whole of intrapartum care, NICE has illustrated this with the aspects concerning postnatal management of the baby.15 Some of the literature review supporting this is less detailed than that supporting the directly maternal recommendations. For example, no detailed literature review was felt necessary for the postnatal observation of higher risk babies, in contrast to the detailed evidence review on the use of “injected water papules” for pain relief in labour.

In addition, the referencing of the NICE guidance could be better. For example, it is suggested that women with prelabour rupture of the membranes be told that the risk of serious neonatal infection is doubled from 0.5 to 1.0% (page 206 of the guideline). However, review of the presented evidence suggests the background risk is lower than this, and the relative risk rather higher. Perhaps other evidence for this statement exists but is unreferenced?

NICE guidance on managing the infant born through MSAF appears to be another such case in point. The text (page 25) carries the unreferenced suggestion that airway suction should be carried out “if the baby has thick or tenacious meconium present in the oropharynx”. Conventional practice is to suction only those babies who are either obtunded or have airway obstruction.1 5 6 8 Furthermore, the guideline understates the association between the thickness of meconium and the subsequent risk of MAS. In the work of Wiswell et al1 work a strong relationship between consistency and outcome was seen.

In The Netherlands postnatal hospitalisation for 24 h appears to have been accepted practice.9 NICE has not issued guidance beyond 12 h of hospitalisation, but for babies born through “thick” meconium do recommend that a rigid programme of observations are carried out at 1, 2, 4, 6, 8, 10 and 12 h in each of 10 domains15 (page 25). Even if we could operationally define “thick” meconium, is such an extensive programme of observations necessary? The paper by Ierland et al9 would suggest not.

Informal polling suggests that few hospitals currently adopt such practices. Perhaps neonatologists are worried that doing such monitoring on as many as an extra 5% of their babies might take their midwives away from the important task of supporting breastfeeding on the postnatal wards? However, we should be aware that English hospital trusts have a strong preference for NICE compliance, making dissent something that needs to be justified at board level.

Would the development of such guidance, considering the costs and challenges of its implementation, be better if it were more forensic in its drafting? NICE has offered guidance on management of the baby when, arguably, we did not know what best practice was. Ierland and colleagues9 have now brought us a little nearer the light. In future, if we don’t yet know, perhaps no guidance would be better than NICE guidance?

REFERENCES

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Footnotes

  • Competing interests None.

  • Provenance and Peer review Commissioned; internally peer reviewed.

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