As with many other pregnancy complications, there is a question of best practice relating to whether women with suspected fetal macrosomia (birthweight >4,000g) should be induced. Affecting around 10 per cent of pregnancies, macrosomia may be associated with longer labours, maternal trauma and an increased likelihood of needing a caesarean section or instrumental delivery. For the baby, there may be an increased riskA way of expressing the chance of an event taking place, expressed as the number of events divided by the total number of observations or people. It can be stated as ‘the chance of falling were one in four’ (1/4 = 25%). This measure is good no matter the incidence of events i.e. common or infrequent. of birth injuries, neonatal complications and of longer term adverse effects, such as cardiovascular disease and diabetes. However, it is unclear whether having a policy of induction affects these risks and improves outcomesOutcomes are measures of health (for example quality of life, pain, blood sugar levels) that can be used to assess the effectiveness and safety of a treatment or other intervention (for example a drug, surgery, or exercise). In research, the outcomes considered most important are ‘primary outcomes’ and those considered less important are ‘secondary outcomes’.. Fetal weight estimation is not very accurate and induction may prove to have been unnecessary.
The review
A Cochrane Review exploring the impact of a policy of labour induction for suspected fetal macrosomia on outcomes for mothers and babies has now been updated. The inclusion of a large, high quality randomized controlled trialA trial in which the people taking part are randomly divided into groups. A group (the intervention group) is given the intervention being tested (for example a drug, surgery, or exercise) and compared with a group which does not receive the intervention (the control group). (RCT) has changed the conclusions of the original review.
The Cochrane ReviewCochrane Reviews are systematic reviews. In systematic reviews we search for and summarize studies that answer a specific research question (e.g. is paracetamol effective and safe for treating back pain?). The studies are identified, assessed, and summarized by using a systematic and predefined approach. They inform recommendations for healthcare and research. includes four RCTs with 1,190 non-diabetic pregnant women with suspected macrosomic babies and no other indications for induction. Induction of labour at 37 to 40 weeks was compared with expectant management. The newly added studyAn investigation of a healthcare problem. There are different types of studies used to answer research questions, for example randomised controlled trials or observational studies. is by far the largest, a multi-centre trialA trial conducted at several geographical sites. Trials are sometimes conducted among several collaborating institutions, rather than at a single institution - particularly when very large numbers of participants are needed. carried out between 2002 and 2009 in Switzerland, France and Belgium (19 hospitals, 822 women). In this trial, labour was induced at 37+0 and 38+6 weeks; methods of induction varied. The other trialsClinical trials are research studies involving people who use healthcare services. They often compare a new or different treatment with the best treatment currently available. This is to test whether the new or different treatment is safe, effective and any better than what is currently used. No matter how promising a new treatment may appear during tests in a laboratory, it must go through clinical trials before its benefits and risks can really be known. were small, carried out in the 1990s in the UK, US and Israel.
What they found
Induction of labour made no clear difference to caesarean section or instrumental delivery rates. More women in the induction group had third- and fourth-degree perineal tears.
On average, babies weighed 178g less when labour was induced, compared with those born without induction. There were fewer fractures in the induction group (four in 1,000 babies compared with 20 in 1,000); therefore, 60 women would need to be induced to prevent one fracture. Fewer in the induction group had shoulder dystocia. There was no clear difference between groups for low Apgar score, low arterial cord pH, or brachial plexus injury –although the trials were too small to show any meaningful change in the incidenceThe number of new occurrences of something in a population over a particular period of time, e.g. the number of cases of a disease in a country over one year. of this rare event. There was no information about mothers’ pain or sexual function, nor about long-term disability in children.
Quality of the evidence
Overall, the quality of the evidenceThe certainty (or quality) of evidence is the extent to which we can be confident that what the research tells us about a particular treatment effect is likely to be accurate. Concerns about factors such as bias can reduce the certainty of the evidence. Evidence may be of high certainty; moderate certainty; low certainty or very-low certainty. Cochrane has adopted the GRADE approach (Grading of Recommendations Assessment, Development and Evaluation) for assessing certainty (or quality) of evidence. Find out more here: https://training.cochrane.org/grade-approach was mixed and, since both the women and their health professionals knew whether induction was happening, that could have affected the results. The evidence was graded as high quality for fracture, moderate for caesarean section and cord pH, and low for instrumental delivery, Apgar score and brachial plexus injury. The evidence on perineal damage is limited.
What next?
The review authors note that there are risks and benefits with induction, which practitioners and clients will need to weigh up, and that these will differ depending on the gestation at which labour is induced. They call for future trials to focus on improving the identification of macrosomic babies and establishing the best time to induce labour.
Reflections on the review, by Alys Einion
The review by Boulvain et al (2016) sets out to evaluate whether routine induction of labour for women with babies who are suspected to be macrosomic would affect mode of birth and morbidityillness or harm for mother or child. This topic is an important one for midwives and for obstetricians. It can be difficult for professionals to advise what is best practice in this area (Caughey 2015) because the evidence is not conclusive and there are benefits and risks to either carrying out induction or not carrying it out.
This leads to challenges for midwives and obstetricians in supporting women with decision-making. Decision-making in pregnancy is always a complex issue. As Vlemmix et al (2013: 257) state, “many decisions in health care do not have a single best option but rather a number of ‘close call’ decisions that are ultimately influenced by patient preference.” Thus, whilst this review provides a helpful insight into risks and benefits related to induction of labour for macrosomia, it cannot provide a black and white answer.
Implications for practice
Difficulties in offering advice
This is a difficult clinical issue. The review seems to echo other work that shows how difficult it is to make decisions and offer recommendations for women with babies who are estimated to be large for gestational age (macrosomic). The Cochrane Review by Boulvain et al (2016) shows that there is a challenging balance between the risks and benefits of induction of labour. If there is no clear difference between induction and expectant management in relation to the likelihood of having a caesarean or instrumental birth, we cannot recommend induction as a means of avoiding the risks of an operative birth. We know that routine caesarean is not recommended for macrosomia (Ozmen et al, 2012).
Timing
If induction of labour decreases the incidence of fractures and shoulder dystocia then surely this would be evidence in favour of routine induction. However, the review shows that “the exact gestation at which doctors and parents will decide on induction cannot be specified from these dataData is the information collected through research.” (Boulvain et al, 2016: 17). This level of uncertainty can be a challenge for clients when trying to make such difficult decisions.
Perineal trauma
And as the review also shows that there is a potential increase in the incidence of significant perineal trauma (third- and fourth-degree tears), which have a major impact on women’s morbidity and quality of life, this has to be taken into account. Whilst not all women experience negative symptoms after repair of this kind of perineal trauma, a review of qualitative evidence shows that there are complex physical and psychological effects, including effects on sexual identity and social marginalization (Priddis et al, 2013).
Discussions need to be individualized
The approach taken by the authors of the review is to state that “the evidence justifies a policy of telling women about these advantages” (the reduction of mean birthweight and birth fractures) (Boulvain et al, 2016: 17). Thus, it would seem that any clinician would need to have a frank conversation about this issue, and each case would need to be approached individually. This would have to include not only the relevant discussion of potential risk-benefit ratios, but also a discussion of the limitations of current approaches to estimating fetal weight.
Problems with estimating fetal weight
One of the key issues that seem to emerge is that in the literature relating to this topic, there is a repeated discussion of the fact that estimation of fetal weight antenatally remains a challenge. Caughey (2015: 2558) states that “clinicians need to consider carefully how estimated fetal weight is measured” but it is clear from the review, and from other studies, that this is an area that needs much more research. Boulvain et al (2016) acknowledge that current methods of estimating fetal weight are poor and that this should be taken into consideration when developing policies relating to routine induction for fetal macrosomia. The National Institute for Health and Care Excellence (NICE) guideline on inducing labour states that “in the absence of any other indications, induction of labour should not be carried out simply because a healthcare professional suspects a baby is large for gestational age (macrosomic)” (NICE 2008: 13).
Conclusion
Thus, the strongest recommendation that emerges from this review is that decisions must be individualized and consider the relative risks and benefits of induction relating to gestational age and potential outcomes. It is clear that until improvements in fetal weight estimation are made, this will continue to be a difficult decision-making process. However, the Cochrane summary infographic provided to summarize this evidence for lay people is a very useful resource for midwives and for clients to help in this.
Join @CochraneUK for a #WeCATS (Critical Appraisal Twitter Session) tweetchat on Twitter on 7th July at 8pm, when we’ll be looking at this Cochrane Review. Join using the #WeCATS hashtag. More information here
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Induction of labour for suspected fetal macrosomia: review and reflections by Sarah Chapman and Alys Einion is licensed under a Creative Commons Attribution-No Derivatives 4.0 International License.
Based on a work at http://www.cochrane.org/CD000938/PREG_induction-labour-or-near-end-pregnancy-babies-suspected-being-very-large-macrosomia.
Permissions beyond the scope of this license may be available at http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD000938.pub2/full. Images have been purchased for Evidently Cochrane from istock.com and may not be reproduced.
Links:
, , , . Induction of labour at or near term for suspected fetal macrosomia. Cochrane Database of Systematic ReviewsIn systematic reviews we search for and summarize studies that answer a specific research question (e.g. is paracetamol effective and safe for treating back pain?). The studies are identified, assessed, and summarized by using a systematic and predefined approach. They inform recommendations for healthcare and research. 2016, Issue 5. Art. No.: CD000938. DOI: 10.1002/14651858.CD000938.pub2. http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD000938.pub2/full
Plain language summary of this review: http://www.cochrane.org/CD000938/PREG_induction-labour-or-near-end-pregnancy-babies-suspected-being-very-large-macrosomia
Caughey AB. Should pregnancies be induced for impending macrosomia? Lancet 2015; 385: 2557-8.
National Collaborating Centre for Women’s and Children’s Health, National Institute for Health and Clinical Excellence. Induction of labour. London: Royal College of Obstetricians and Gynaecologists; 2008. (NICE CG70). [Issued July 2008]. Available from: http://tinyurl.com/zrmjx3a
Ozmen B, Sukur YE, Yuce T, Bayramov V, Olmus H, Sonmezer M, Atabekoglu CS. Mode of delivery and birth complications in fetal macrosomia: a simple cost-effectiveness analysis. Turkish Journal of Medical Sciences 2012; 42(1): 119-25.
Priddis H, Dahlen H, Schmied V. Women’s experiences following severe perineal trauma: a meta-ethnographic synthesis. Journal of Advanced Nursing 2013; 69(4): 748–59.
Vlemmix F, Warendorf J, Rosman A, Kok M, Mol BW, Morris JM, Nassar N. Decision aids to improve informed decision-making in pregnancy care: a systematic review. BJOG: An International Journal of Obstetrics and Gynaecology 2013; 120: 257–66.
