intrauterine growth restriction

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Intrauterine growth restriction (IUGR) or fetal growth restriction (FGR) is defined as an estimated fetal weight (EFW) / abdominal circumference (AC) at one point in time during pregnancy being below 3 percentile or EFW/AC below the 10 percentile for gestational age with deranged Doppler parameters .

An IUGR can be broadly divided into two main types:

type I: symmetrical intrauterine growth restriction
type II: asymmetrical intrauterine growth restriction

Some authors also enlist a third type termed: femur-sparing intrauterine growth restriction .

Pathology

Etiology

IUGR can result from a vast number of causes:

maternal conditions
- maternal narcotics/smoking
- maternal alcohol use: fetal alcohol syndrome
- maternal diabetes: when severe maternal diabetes, there can be a paradoxical IUGR as opposed to fetal macrosomia
- maternal malnutrition/starvation
- maternal vascular conditions
- certain medications
placental insufficiency: commonest cause overall
- abnormal uteroplacental circulation
- abnormal fetoplacental circulation
other placental causes
- increased incidence with a single umbilical artery
fetal conditions
- multifetal pregnancy
- intrauterine infections
- chromosomal anomalies
  - trisomy 13
  - trisomy 18
  - triploidy: IUGR is of early-onset
  - Down syndrome: not a dominant feature
  - chromosome 4p deletion syndrome (Wolf-Hirschhorn syndrome)
  - chromosome 12p tetrasomy (Pallister-Killian syndrome)
- confined placental mosaicism (CPM)
- other syndromic anomalies
- in utero substance exposure
  - e.g. fetal hydantoin syndrome

Radiographic features

Antenatal ultrasound

Sonographic parameters include:

non-Doppler features
- reduced abdominal circumference (AC) and/or EFW
  - AC/EFW <3 percentile
  - AC/EFW <10 percentile with deranged Doppler parameters
- presence of oligohydramnios without ruptured membranes
- increased head circumference (HC) to abdominal circumference (AC) ratio (in asymmetrical type)
- advanced placental grade
Doppler features: will require a chart to calculate absolute values
- umbilical artery Doppler assessment
  - increased PI above 95 percentile
  - absent/reversed diastolic flow
- umbilical venous Doppler assessment
  - presence of pulsatility
- uterine arterial Doppler assessment
  - increased mean uterine artery PI above 95 percentile
  - presence of notching in mid to late pregnancy
- CP ratio: reduced below 5 percentile

Treatment and prognosis

While there is no cure, management is reliant on a structured antenatal surveillance program with timely intervention in order to minimize fetal compromise.

Complications

There are many including:

antepartum
- stillbirth
- iatrogenic prematurity
- abruption
- perinatal stroke
intrapartum
- abnormal fetal status (fetal heart rate tracing)
- asphyxia
- emergency Cesarean section
- need for active neonatal resuscitation
- perinatal stroke
neonatal
- hypothermia
- hypoglycemia
- hypocalcemia
- polycythemia
- sepsis
- coagulopathy
- hepatocellular dysfunction
- respiratory distress syndrome
- necrotizing enterocolitis
- intraventricular hemorrhage, especially in premature IUGR neonates <750 g
- hypoxic-ischemic encephalopathy
pediatric
- increased risk of:
  - short stature
  - cerebral palsy
  - developmental delay
  - behavioral and emotional problems
  - lower IQ scores
  - chronic lung disease
  - future cardiovascular disease and hypertension

Differential diagnosis

General considerations include:

incorrect dates