Reply

Abstract

Drs Schreurs, Mol and de Boer have raised some doubts regarding the use of a Delphi consensus procedure in establishing a diagnosis of fetal growth restriction (FGR), claiming that empirical evidence can be found to diagnose and thus define FGR. We agree fundamentally that empirical evidence in this patient group is necessary and that such evidence should be instrumental in further refining the definition of FGR. Indeed, ideally a definition would be derived wholly from conditions that are associated with adverse fetal and neonatal outcomes. Long-term childhood outcomes would be even better, because this is the real concern for parents. However, such evidence is currently lacking. In the absence of a uniform definition, many different definitions are used in the literature, and most of these simply define small-for-gestational age (SGA) rather than FGR. There is no gold standard for the definition of FGR at the present time. One of the obstacles relates to the differential expression of growth abnormalities across gestation. Our aim was neither to define the pathway or pathophysiological mechanism, nor to come to a prediction model; our aim was to develop a definition that helps focus clinical work and research on those fetuses most likely to have the problem of interest. There is an increasing appreciation in the FGR community that studies should focus more on the fetuses at risk and that this may be feasible by introducing functional parameters1, 2. The association between these parameters and fetal risk is already known, although the strength of these associations still needs further study. The Delphi procedure uses the existing knowledge and beliefs among FGR experts to better estimate the disease of interest, despite the limited evidence. We strongly agree with Schreurs et al. about the need for diagnostic and intervention studies. Nevertheless, our use of the Delphi consensus procedure advocates and facilitates some uniformity in the target population, thus allowing these studies to be as focused as possible, and ensuring that promising tests that work for FGR but not for SGA are not discarded. Whilst we await empirical evidence to define FGR, we have provided a workable alternative with a proper basis. Our expert panel was selected carefully, our level of agreement was high (70%) and we double-checked every conclusion. Having an established definition is a starting point for further studies on FGR and allows better synthesis of existing evidence. In order for investigators to work together and compare data it is necessary to standardize nomenclature so that everyone is using the same language. Future studies may indicate that other parameters merit introduction into the definition, or that other cut-offs better identify the fetuses at risk, and we look forward to reconsidering the definition as new evidence emerges. S. J. Gordijn, on behalf of the coauthors Department of Obstetrics and Gynecology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands (e-mail: s.j.gordijn@umcg.nl)