Intrauterine fetal growth restriction (IUGR)

1. Small in size does not equate intrauterine fetal growth restriction
Assessment of the fetal growth is an essential part of antenatal care. There are several reasons for the fetus to be small for the gestational age:

  • Date problem- some error in the calculation of the maturity (gestational age) of the pregnancy. The most accurate way for calculation of maturity is by an early ultrasound at 6-9 weeks of gestation
  • Constitutionally small baby: sometimes the fetus is smallish because the mother is also of a small build
  • Normal variation: babies with size below the normal range can still be normal variants
  • Intrauterine fetal growth restriction (IUGR)

2. 3 reasons for IUGR

  • Placental cause – the sub-optimal placenta function
  • Maternal cause – vascular diseases, smoking, malnutrition, alcohol or drugs
  • Fetal cause – chromosomal anomalies, genetic conditions, or infection

3. Early onset IUGR in second trimester

  • Early onset IUGR in the second trimester is not as common as in the third trimester but is usually of poorer prognosis
  • Higher chance of fetal causes including chromosomal, genetic or infective causes. Amniocentesis and infection screening should be considered
  • Could also be placental cause as an early sign of placental failure or pre-eclampsia

4. IUGR in the third trimester

  • Most IUGR are discovered in the late pregnancy
  • Relatively higher chance of placental cause compared with early onset IUGR
  • Serial ultrasound monitoring is indicated: for fetal growth, liquor volume and doppler ultrasound for fetal wellbeing
  • Consider earlier delivery if complete absence of fetal growth or abnormal fetal wellbeing on doppler studies. It is a fine balance between the risks of intrauterine fetal damage versus iatrogenic prematurity


5. Mode of delivery for IUGR

  • Induction of labour with careful fetal heart monitoring is a legitimate option provided the cervical status is favourable and the fetus has remained in good condition
  • Caesarean section should be considered if very unfavourable cervix and/ or signs of severe fetal compromise already on doppler scan
This article is contributed by Dr. T.N. Danny Leung
Updated on 30.09.2020