Paeds · fetal-neonatal-and-perinatal
Fetal growth restriction and small-for-gestational-age infant
Also known as Intrauterine growth restriction (IUGR) · Small for gestational age · Fetal growth restriction · SGA infant · Placental insufficiency
Fellowship guide to distinguishing fetal growth restriction from the constitutionally small infant, antenatal surveillance and Doppler interpretation, and the early neonatal management of hypothermia, hypoglycaemia, polycythaemia and feeding difficulty.
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Target exams
Red flags
- Absent or reversed end-diastolic flow on umbilical artery Doppler
- Symptomatic or persistent neonatal hypoglycaemia despite feeding and buccal gel
- Polycythaemia with hyperviscosity signs — lethargy, poor feeding, seizures
- Perinatal depression, low Apgar or cord acidosis in a growth-restricted infant
- Dysmorphism, structural anomaly or stigmata of congenital infection in a small neonate
- A growth velocity that falls across centiles even if the infant is not yet below the 10th
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Board mappings
- Neonatal and Perinatal Medicine
- General and Community Paediatrics
- Current 2026 PREP curriculum — Learning Objective 1.1.2: Assess and manage fetal compromise and the newborn infant with perinatal risk factors
- Current 2026 PREP curriculum — Learning Objective 2.1.3: Assess and manage the growth-restricted fetus and small-for-gestational-age neonate
- Renewed curriculum for first-year trainees from 2027 — Learning goal 5: Clinical assessment – essential general paediatrics
- Renewed curriculum for first-year trainees from 2027 — Learning goal 6: Clinical management – essential general paediatrics
- Renewed curriculum for first-year trainees from 2027 — Learning goal 11: Acute care and procedures
- Renewed curriculum for first-year trainees from 2027 — Learning goal 15: Essential general paediatrics
- Medical Sciences
- Long Cases
- Short Cases
- 1. Neonatal medicine: Assessment and management of the growth-restricted fetus and small-for-gestational-age neonate
- 4. Professional skills and knowledge: Patient management
- 5. Early detection and management of acutely ill children
- 7. Patient safety, including safe prescribing
- Foundation of Practice (FOP)
- Theory and Science (TAS)
- Applied Knowledge in Practice (AKP)
- Clinical
- History
- Development
- Communication
- General Pediatrics Content Outline — Domain 2: Fetal and Neonatal Care
- General Pediatrics Content Outline — Domain 18: Endocrinology (growth)
- General Pediatrics Content Outline — Universal Task 1: Physiology and Pathophysiology
- General Pediatrics Content Outline — Universal Task 3: Diagnosis
- Patient Care 3: Organize and Prioritize Patient Care
- Patient Care 4: Clinical Reasoning
- Patient Care 5: Patient Management
- Medical Knowledge 1: Core signs and symptoms of disease
- Medical Expert
- Neonatal-Perinatal Medicine
- Pediatrics: Foundations EPA #1 — Recognizing deteriorating and/or critically ill patients and initiating stabilization and management
- Pediatrics: Foundations EPA #4 — Providing care to a healthy newborn
Two different small babies
Constitutionally small (healthy SGA)
Fetal growth restriction (pathological)
Overview & Definition
Meet a common scenario. A baby is born at term weighing 2350 g — below the 10th centile. The midwife calls the baby "small for dates". Before you reach for tests or admit to NICU, ask one question that changes everything: is this baby small because they are meant to be small, or because something went wrong in utero? [3]
That single distinction — between the constitutionally small infant and the growth-restricted infant — is the whole of this topic. [1]
Small for gestational age (SGA) is a size label. It means the birthweight (or the antenatal estimated fetal weight) is below the 10th centile for gestational age and sex on a standard chart. [3] About one baby in ten carries the label by definition. Severe SGA is below the 3rd centile. None of this tells you why the baby is small.
Fetal growth restriction (FGR) is a process. The fetus has failed to reach the size it was genetically programmed to achieve, because it was deprived of nutrients or oxygen — most often by a failing placenta. [1] Many FGR fetuses are also SGA, but not all. A fetus whose growth falls from the 60th to the 15th centile is growth-restricted even though it never crosses the 10th, and a perfectly healthy small baby can sit comfortably below the 10th all pregnancy.
So the terms overlap like two circles that do not sit perfectly on top of each other. Most SGA babies are healthy and constitutionally small. Some are pathologically growth-restricted. And a few growth-restricted babies are not (yet) below the 10th centile. Your job at the bedside and in the long case is to work out which circle each baby sits in. [2]
References14ShowHide
- [1]Gordijn SJ Consensus definition of fetal growth restriction: a Delphi procedure. Ultrasound in Obstetrics & Gynecology, 2016.PMID 26909664
- [2]Figueras F Update on the diagnosis and classification of fetal growth restriction and proposal of a stage-based management protocol. Fetal Diagnosis and Therapy, 2014.PMID 24457811
- [3]Villar J International standards for newborn weight, length, and head circumference by gestational age and sex: the Newborn Cross-Sectional Study of the INTERGROWTH-21st Project. Lancet, 2014.PMID 25209487
- [4]Papageorghiou AT International standards for fetal growth based on serial ultrasound measurements: the Fetal Growth Longitudinal Study of the INTERGROWTH-21st Project. Lancet, 2014.PMID 25209488
- [5]Villar J The likeness of fetal growth and newborn size across non-isolated populations in the INTERGROWTH-21st Project: the Fetal Growth Longitudinal Study and Newborn Cross-Sectional Study. The Lancet Diabetes & Endocrinology, 2014.PMID 25009082
- [6]Lees CC Perinatal morbidity and mortality in early-onset fetal growth restriction: cohort outcomes of the trial of randomized umbilical and fetal flow in Europe (TRUFFLE). Ultrasound in Obstetrics & Gynecology, 2013.PMID 24078432
- [7]Lees CC 2 year neurodevelopmental and intermediate perinatal outcomes in infants with very preterm fetal growth restriction (TRUFFLE): a randomised trial. Lancet, 2015.PMID 25747582
- [8]Ganzevoort W How to monitor pregnancies complicated by fetal growth restriction and delivery before 32 weeks: post-hoc analysis of TRUFFLE study. Ultrasound in Obstetrics & Gynecology, 2017.PMID 28182335
- [9]Ganzevoort W Comparative analysis of 2-year outcomes in GRIT and TRUFFLE trials. Ultrasound in Obstetrics & Gynecology, 2020.PMID 31125465
- [10]Crispi F Long-term cardiovascular consequences of fetal growth restriction: biology, clinical implications, and opportunities for prevention from birth. American Journal of Obstetrics and Gynecology, 2018.PMID 29422215
- [11]Victora CG, Villar J, Barros FC, et al. Anthropometric characterization of impaired fetal growth: risk factors for and prognosis of newborns with stunting or wasting. JAMA Pediatrics, 2015.PMID 26147058
- [12]McKinlay CJ Neonatal glycemia and neurodevelopmental outcomes at 2 years. New England Journal of Medicine, 2015.PMID 26465984
- [13]McKinlay CJD Association of neonatal glycemia with neurodevelopmental outcomes at 4.5 years. JAMA Pediatrics, 2017.PMID 28783802
- [14]Paules C Premature placental aging in term small-for-gestational-age and growth-restricted fetuses. Ultrasound in Obstetrics & Gynecology, 2019.PMID 30125412