Intrauterine growth restriction

Intra-uterine growth restriction (IUGR) is commonly defined as an estimated fetal weight (EFW) at one point in time during pregnancy being at or below the 10^th percentile for gestational age ².

Some authors define the term IUGR when fetal biometric parameters fall under the 5^th centile or fall below two standard deviations ¹².

Some authors consider this definition synonymous with the term small for gestational age (SGA).

An IUGR can be broadly divided into two main types:

• type I: symmetrical intra-uterine growth restriction
• type II: asymmetrical intra-uterine growth restriction

Some authors also enlist a 3^rd type termed: femur sparing intra-uterine growth restriction ¹⁰.

Epidemiology

By its standard definition itself, it carries a prevalence of 10% of all births (if the 5^th centile is used it will affect 5% of all births instead).

Pathology

Causes

IUGR can result from a vast number of causes:

• maternal conditions
  • maternal narcotic/alcohol use/smoking
  • maternal diabetes: when the maternal diabetes severe, 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 utero-placental circulation
  • abnormal feto-placental circulation
• other placental causes
  • increased incidence with a single umbilical artery
• fetal conditions
  • multifetal pregnancy
  • intra-uterine infections
  • chromosomal anomalies
    • trisomy 13
    • trisomy 18
    • triploidy: IUGR is of early onset
    • Down syndrome: not a dominant feature
    • chromosome 4p deletion syndrome
  • confined placental mosaicism (CPM) ¹³
  • other syndromic anomalies
    • Neu-Laxova syndrome
    • Pena Shokeir syndrome
    • Seckel syndrome
    • Smith-Lemli-Opitz syndrome
  • in utero substance exposure
    • e.g. fetal hydantoin syndrome

Radiographic features

Antenatal ultrasound

Sonographic parameters include:

• non Doppler features
  • presence of oligohydramnios without ruptured membranes
  • increased head circumference (HC) to abdominal circumference (AC) ratio (in asymmetrical type)
  • decreased total intrauterine volumes
  • advanced placental grade
• Doppler features: will require a chart to calculate absolute values
  • umbilical artery Doppler assessment 
    • increased S/D ratio(s)
    • increased resistive index (RI)
  • umbilical venous Doppler assessment
    • presence of pulsatility
  • uterine arterial Doppler assessment
    • presence of notching in mid to late pregnancy
    • increased S/D ratio(s)

Complications

They are many which include:

• chronic fetal hypoxaemia ⁶
• neurodevelopmental delay

ManagementTreatment 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.

Differential diagnosis

General considerations include:

• incorrect dates

See also

• small for dates fetus