American Journal of Obstetrics and Gynecology
Expert ReviewEvidence-based national guidelines for the management of suspected fetal growth restriction: comparison, consensus, and controversy
Introduction
Small for gestational age (SGA) is usually defined as an infant with a birthweight for gestational age <10th centile for a population1, 2 or customized standard.3, 4 These definitions of SGA will include a proportion of babies (18-22%) who are constitutionally small but healthy.4, 5 Fetal growth restriction (FGR) generally refers to a fetus that has failed to reach its biological growth potential because of placental dysfunction.6 FGR has considerable overlap with SGA but is more difficult to define in practice, as not all FGR infants have a birthweight <10th centile.7, 8, 9
Suboptimal fetal growth is important as SGA babies comprise 28-45% of nonanomalous stillbirths.10, 11 Placental insufficiency is a major contributor to the pathophysiology in SGA pregnancies and contributes to the adverse perinatal outcomes.12 Infants born SGA have higher rates of neurodevelopmental delay, poor school performance, childhood and adult obesity, as well as metabolic disease.13, 14, 15, 16, 17, 18 A limitation of current antenatal care is that the majority of SGA pregnancies are not identified before birth.19, 20, 21 SGA infants recognized before birth who undergo surveillance and timely delivery have a 4- to 5-fold reduction in mortality and/or severe morbidity.22, 23 Therefore, many SGA stillbirths are preventable if detection could be improved and management optimized.
Internationally and regionally, detection of SGA and management approaches can vary considerably. Only 2 previous publications have compared SGA management guidelines between countries.24, 25 The first by Chauhan et al24 compared the now obsolete 2000 American Congress of Obstetricians and Gynecologists (ACOG) guidelines with the 2002 Royal College of Obstetricians and Gynecologists (RCOG) United Kingdom guidelines and noted that there were considerable variations in content, references cited, and recommendations. More recently, Unterscheider et al25 compared recommendations made in 4 national guidelines but did not include the New Zealand or the French guideline. The aim of this review is to summarize areas of consensus and controversy between recently published national guidelines on SGA or FGR; to highlight any recent evidence that should be incorporated into existing guidelines; and to identify future research priorities in this field.
Section snippets
Materials and Methods
Searches through MEDLINE and Google were performed to identify national guidelines on management of pregnancies complicated by FGR/SGA. MEDLINE searches were undertaken using the terms: “fetal growth retardation/or fetal growth restriction,” “small for gestational age,” and “clinical practice guideline.” The search was confined to articles published from 2010 and published in English. The last search was undertaken on Aug. 7, 2017. Four relevant national guidelines were identified through this
Results
National guidelines from 6 countries were identified that met the above criteria. These were produced in the United States (ACOG27 and Society for Maternal-Fetal Medicine28); the United Kingdom (RCOG29); Canada (Society of Obstetricians and Gynecologists of Canada30); New Zealand (New Zealand Maternal Fetal Medicine Network31); Ireland (Health Service Executive32); and France (French College of Gynecologists and Obstetricians33). The process for guideline development is summarized in Table 1.
Definitions of FGR
All guidelines recommended that EFW <10th centile is an appropriate definition of FGR, with some requiring additional parameters to confirm pathological growth restriction. Incorporation of a measure of reduced growth velocity was inconsistent, included in 4 of 6 guidelines (67%),29, 31, 32, 33 but often without a specific definition. A recently published Delphi survey on definition of FGR, that incorporated responses from 45 experts, reached a consensus definition of early- and late-onset FGR
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The authors report no conflict of interest.