Intra-uterine growth restriction (IUGR), also referred to as fetal growth restriction, is a condition in which a baby doesn’t grow to a normal weight during the pregnancy. This means that the baby is smaller than expected for the number of weeks of pregnancy.
A percentile chart is used to plot the fetal growth during a pregnancy and the weight will be less than the 10th percentile, which means that the baby weighs less then 9 out of 10 babies at the same gestational age.
Growth restriction can begin at any time of the pregnancy and affects about 10% of pregnancies.
- Low birth weight: baby’s birthweight is less than 2 500g.
- Small for gestational age: baby’s birthweight is below the 10th percentile for the pregnancy duration, this can be due to growth restriction or a genetically small baby.
- Intra-uterine growth restriction: baby’s birthweight is below the 10th percentile and shows clinical signs of growth restriction.
- Symmetrical IUGR: all parts of the baby/fetus are similarly small.
- Asymmetrical IUGR: the baby’s head and brain are the expected size, but the rest of the body is smaller than expected.
What causes IUGR?
Often the main cause of growth restriction is the decreased supply of nutrients and blood to the baby. This is primarily caused by a problem with the umbilical cord or the placenta. Causes include:
- placental conditions
- a knot in the cord or abnormal cord insertion
- multiple pregnancies: twins or triplets that may share a placenta.
- pre-eclampsia or other causes of raised blood pressure
- heart disorders, diabetes, anaemia, autoimmune conditions
- malnutrition of the mother: hyperemesis gravidarum, anorexia, poor nutrition
- substance use: alcohol, cigarette use, drugs
- intra-uterine infections
- genetic/chromosomal abnormalities of the baby
How is IUGR diagnosed and managed?
One of the main reasons for antenatal visits is to check the growth of the fetus. There might be poor or no weight gain of the mother. The measurement of the abdominal size will often be smaller than expected for the gestational age.
Ultrasound measures the estimated fetal weight, calculates the amount of amniotic fluid, and measures the blood flow through the umbilical cord (doppler ultrasound). Plotting the weight of the baby on the centile chart, will give an accurate evaluation of the fetal growth and wellbeing.
Management depends on the severity of the growth restriction and the gestational age in which it occurs.
- Frequent monitoring of the baby’s growth via ultrasound.
- Tracking fetal movements.
- Determine the underlying cause and treat if possible: discontinuation of substances, controlling high blood pressure, well balanced diet.
- Corticosteroids to improve the baby’s lung maturity in the case of an early delivery.
- Early delivery: if the baby is not growing an earlier delivery may be safest. This can be done via an induction, but often requires a caesarean section, as a vaginal delivery can stress a growth-restricted baby.
Consequences of IUGR
There is an increased risk for a premature delivery and delivery via caesarean section in cases of growth restriction. Growth restricted neonates may have issues breathing and feeding, regulating their body temperature, and maintaining their blood sugar.
Often extra time is needed in the hospital or the neonatal unit. Commonly growth restricted babies will catch up once receiving adequate nutrition. If the growth restriction was very severe, there is an increased risk of developmental delay and cardiovascular disease later in life. There is a 20-30% risk of recurrence in a future pregnancy.