11/14/24, 10\:59 AM Intrauterine Growth Restriction (IUGR)

Intrauterine Growth Restriction (IUGR)

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Key points ⚡
Succinct notes to superpower your revision
Intrauterine growth restriction (IUGR)\: foetus does not grow to its genetic potential in the uterus; increased risk of
morbidity and mortality.
SGA vs IUGR\: SGA is a foetus with AC or EFW \< 10th centile; may be small but not at increased risk. IUGR involves
pathological growth restriction with increased risk of foetal compromise.
Asymmetrical IUGR\: disproportionate growth restriction (decreased body and limbs vs. head); caused by extrinsic factors
like placental insu
Symmetrical IUGR\: proportional growth restriction in all parts; caused by intrinsic factors like genetic abnormalities or
infections; a
Risk factors\:
Maternal\: diabetes, hypertension, lupus, substance use, teratogenic drugs, previous IUGR pregnancy.
Uteroplacental\: placental insu
abnormalities, multiple gestation.
Foetal\: infections (toxoplasmosis, CMV, etc.), genetic abnormalities, congenital anomalies.
Clinical features\:
History\: assess risk factors, symptoms of underlying causes (e.g., abdominal pain in placental abruption, headache in pre-
eclampsia).
movements.
Examination\: decreased SFH (≥3cm less than gestational age), small for gestational age foetus, reduced/absent foetal
Investigations\:
Bedside\: maternal vital signs, urine dipstick, CTG (late decelerations, bradycardia).
Laboratory\: tests based on suspected cause (e.g., OGTT for gestational diabetes, serology for infections).
Imaging\: serial ultrasound (foetal biometry, placental morphology, amniotic
diastolic
Diagnosis\: serial ultrasound and UA Doppler showing EFW \<10th centile, oligohydramnios, abnormal UA Doppler, poor
interval growth velocity, and/or EFW \<3rd centile.
Management\:
Conservative\: optimise modi
Medical\: treat underlying maternal conditions (e.g., gestational diabetes, pre-eclampsia), monitor maternal and foetal status.
Surgical\: delivery for non-reassuring foetal status/maternal compromise; consider induction of labour or caesarean section,
magnesium sulphate for neural protection (\<33+6 weeks), corticosteroids for foetal lung maturity (24+0 to 33+6 weeks).
Prevention\: manage underlying causes, lifestyle advice (smoking cessation), low-dose aspirin before 16 weeks gestation.
Complications\: preterm labour, stillbirth, perinatal asphyxia, necrotising enterocolitis, cognitive delay, adult-onset diseases,
motor and neurological disabilities, intrauterine/neonatal death.
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Introduction

Intrauterine growth restriction (IUGR), also known as foetal growth restriction (FGR), is when a foetus does not grow to its
genetic potential in the uterus. IUGR is associated with an increased risk of morbidity and mortality.
The terms IUGR and small for gestational age (SGA) are often incorrectly used synonymously.
SGA is de
th
centile for its gestational age. The foetus may be constitutionally small without being at increased risk of complications.
In contrast, IUGR is a pathological in-utero growth restriction with an increased risk of foetal compromise.
1,2

Aetiology

Asymmetrical IUGR
Asymmetrical IUGR refers to disproportionate growth restriction with a greater decrease in foetal body and limbs
compared to head circumference. It is caused by extrinsic factors such as placental insu
In asymmetrical IUGR, oxygen and nutrients are directed towards vital foetal organs (brain and heart) bypassing other
organs (e.g. foetal liver, muscle and fat tissue). This a
Symmetrical IUGR
Symmetrical IUGR refers to proportional growth restriction in all parts of the foetus. It is caused by intrinsic factors such
as genetic abnormalities and intrauterine infections. This a

Risk factors

Risk factors for IUGR can be divided into maternal, uteroplacental and foetal risk factors.
Maternal risk factors
Maternal risk factors include\:
Maternal medical conditions\: pre-existing diabetes mellitus, chronic hypertension, gestational hypertension, pre-
eclampsia, systemic lupus erythematosus, antiphospholipid syndrome, sickle cell disease, severe anaemia, anorexia
nervosa
Substance use\: tobacco, alcohol, cocaine, or narcotics
Exposure to teratogenic drugs\: ACE-inhibitors, warfarin, carbamazepine, phenytoin, cyclophosphamide or valproic acid
Previous pregnancy with IUGR
Uteroplacental risk factors
Uteroplacental risk factors include\:
Placental insu
anorexia nervosa) or pregnancy-related conditions (e.g. Rh- incompatibility or pre-eclampsia)
Placenta praevia or placental abruption
Umbilical artery thrombosis or infarction
Uterine abnormalities (e.g.
Multiple gestation
Foetal risk factors
Foetal risk factors include\:
Congenital/early intrauterine infections\: toxoplasmosis, rubella, cytomegalovirus infection, varicella, tuberculosis, herpes
infections, HIV infection, syphilis, or malaria
Genetic abnormalities\: aneuploidy
Congenital anomalies\: tracheoesophageal
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Clinical features

History
A thorough obstetric history is crucial to identify any risk factors for IUGR.
Signs and symptoms will depend on the underlying cause of IUGR. For example, a patient may present with abdominal
pain due to placental abruption or headache, visual disturbances, and epigastric pain due to pre-eclampsia.
Clinical examination
Typical clinical
3
Symphysial-fundal height (SFH) is decreased compared to gestational age (at least 3cm less than gestational age in
weeks)
Foetus is small for gestational age
Foetal movements are reduced or absent

Investigations

Bedside investigations
Relevant bedside investigations include\:
Maternal vital signs (basic observations)\: blood pressure, heart rate, respiratory rate, oxygen saturation, temperature
Urine dipstick
Cardiotocography (CTG)\: to assess foetal compromise. It may show late decelerations of the foetal heart rate and foetal
bradycardia in IUGR.
1
Laboratory investigations
Appropriate laboratory investigations are performed based on the suspected underlying cause of IUGR.
For example, oral glucose tolerance test (OGTT) for gestational diabetes mellitus and serological screening for congenital
intrauterine infections.
Imaging
Relevant imaging investigations include\:
1,4
Serial ultrasound scans\: to assess foetal biometry and estimated foetal weight which are plotted on a customised
growth chart. Ultrasound also provides detailed information on foetal anatomy, placental morphology, and amniotic
volume. Findings may include decreased foetal growth with foetal weight below the 10 th
centile of a given gestational
age, small placenta and oligohydramnios.
Umbilical artery Doppler (UA Doppler)\: shows abnormalities such as reduced or reversed diastolic
Biophysical pro\: is a non-invasive test that integrates di

decreased foetal movements and tone. A BPP score of ≤ 4 indicates the need for delivery.

Diagnosis

The diagnosis of IUGR is made from serial ultrasound scans and umbilical artery Doppler (UA Doppler) showing
estimated foetal weight \<10th centile, oligohydramnios, abnormal UA Doppler and/or poor interval growth velocity and/or
EFW \<3rd centile.
1

Management

Conservative management
Conservative management involves optimising modi
drug counselling, and healthy diet and exercise.
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Medical management
It is important to treat any underlying maternal condition (e.g. treatment of gestational diabetes mellitus or pre-eclampsia)
and medically optimise any co-morbidities before and during pregnancy.
Maternal vital signs should be closely monitored alongside foetal status.
Surgical management/delivery
Delivery should be performed if there are signs indicating non-reassuring foetal status or maternal compromise.
The optimal timing and mode of delivery (either induction of labour or caesarean section) for IUGR require careful
consideration of both maternal and foetal risks of continued intrauterine existence, premature delivery, labour and
caesarean section.
The goal is to delay delivery and prolong intrauterine life to gain foetal maturity, improve survival and reduce the risks of
morbidity and mortality.
1
Induction of labour is o
of foetal compromise such as absent and reduced end-diastolic
1
Magnesium sulphate should be administered in gestations less than 33 +6
delivery is contemplated.
5
weeks for foetal neural protection, where
Prenatal corticosteroids should be administered to women with IUGR foetus between 24 +0 +6
to 33 weeks gestation when
preterm birth is imminent. Corticosteroids should be discussed with women undergoing a planned caesarean section up
until 38 weeks.
+0 1,5
When EFW is \<10th centile and UA Doppler is normal, delivery can be delayed until at least 37 weeks, and even until 38-39
weeks of gestation in some cases.
1,6
Prevention of IUGR
The risk of a recurrent IUGR in a subsequent pregnancy is approximately 25%.
1
Preventative strategies for IUGR include\:
1,6
Reviewing and managing the underlying causes (e.g. maternal co-morbidities)
Lifestyle advice such as smoking cessation and dietary advice
Consider administration of low dose aspirin prior to 16 weeks of gestation

Complications

Complications of IUGR include\:
1,3,4
Preterm labour and delivery
Stillbirth
Perinatal asphyxia
Necrotising enterocolitis
Cognitive delay and behavioural issues
Adult-onset diseases (e.g. diabetes mellitus, obesity, coronary artery disease, hypertension)
Motor and neurological disabilities
Intrauterine/neonatal death
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References

Institute of Obstetricians & Gynaecologists Royal College of Physicians of Ireland. F e t a l G r o w t h R e s t r i c t i o n – R e c o g n i t i o n ,
D i a g n o s i s & M a n a g e m e n t . Published in 2014. Available from\: [LINK]
Patient.info Professional References. I n t r a u t e r i n e G r o w t h R e s t r i c t i o n . Published in 2016. Available from\: [LINK]
UpToDate. Fetal g r o w t h r e s t r i c t i o n \: S c r e e n i n g a n d D i a g n o s i s . Published in 2021. Available from\: [LINK]
AMBOSS. I n t r a u t e r i n e G r o w t h R e s t r i c t i o n . Published in 2021.
National Institute for Health and Care Excellence. P r e t e r m L a b o u r a n d B i r t h . Published in 2015. Available from\: [LINK]
Royal College of Obstetricians & Gynaecologists. F e t u s . Published in 2013. Available from\: [LINK]
T h e I n v e s t i g a t i o n a n d M a n a g e m e n t o f t h e S m a l l -f o r-G e s t a t i o n a l -A ge
The American College of Obstetricians and Gynecologists. F e t a l G r o w t h R e s t r i c t i o n . Published in 2019. Available from\:
[LINK]

Reviewer

Dr Karim Botros
RCSI Honorary Clinical Lecturer
Senior Registrar in Obstetrics & Gynaecology
University Hospital Waterford, Waterford, Ireland

Related notes

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Antenatal Screening for Down’s Syndrome
Antepartum Haemorrhage (APH)
Breech Presentation
Caesarean Section

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Contents

Introduction
Aetiology
Risk factors
Clinical features
Investigations
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