Intrauterine Growth Retardation (IUGR) occurs in around 3-5% of all pregnancies. This is a condition where the baby’s growth is compromised and restricted, so that they are smaller than they should be. By definition, a baby with IUGR weighs below the 10th percentile for their gestational age.
One of the goals of regular antenatal care is to assess if the baby is growing as it needs to be. The mother’s abdominal size is compared with her weeks of gestation. Although individual mothers vary in their tummy size, there are still standard abdominal markers which indicate that the baby is growing. For example, by the end of the first trimester at 12 weeks, the womb should have grown to the level of the mother’s pubic bone and by 20 weeks of gestation, the top of the womb, or fundus, should be at the level of her bellybutton.
Risk Factors for Growth Restriction
Mothers who have poor antenatal education and whose dietary intake is insufficient
Mothers who have previously had a baby who had IUGR
Smoking cigarettes, taking illicit drugs and drinking alcohol are all risk factors for IUGR
Babies who have a chromosomal abnormality such as Down Syndrome, Turner Syndrome or an abnormality of one of their major organs more commonly have IUGR
Babies who have contracted an infection such as rubella, toxoplasmosis or cytomegalovirus while in the womb
Mothers who are unwell themselves or who have had other pregnancy-related complications
Mothers with high blood pressure or preeclampsia
When there is placental insufficiency due to an abnormal placenta or there is placenta praevia
IUGR is more common in twin pregnancies, particularly identical twins
Genetics plays a part: mothers who themselves were small at birth and whose partner was small as well, tend to have smaller babies themselves
What are the Different Types of IUGR?
Symmetrical growth restriction relates to early pregnancy, when the baby’s head and body are both small, this basically means there is an overall stunting of the baby’s growth. This occurs when the baby has had an infection, or has been exposed to different toxic substances such as nicotine, illicit drugs or alcohol.
Asymmetrical growth restriction relates to the period after 20 weeks when the placenta is not working as effectively as it needs to be. This occurs during preeclampsia, in multiple pregnancies and if the baby has an abnormality. It happens more or less as a protective mechanism to protect the baby’s brain and heart and ensure they keep growing. These organs are prioritised because they are essential to the baby’s survival.
However, there is a cost to the rest of the body as the fat stores are used up. Babies with asymmetrical growth restriction look scrawny when they are born. They appear thin and like “little old men”. They tend to have a very worried, hungry face and seem to constantly be hungry.
How is Intrauterine Growth Restriction Diagnosed?
When mothers go for antenatal appointments, their uterine growth is checked through abdominal palpation (feeling with the fingers and hands during a physical examination).
This provides a reasonable guide to whether a baby is growing as it should be. The fundal height i.e. the top of the womb, is measured from the mother’s symphystic pubis (her pubic bone) and this is compared with her weeks of gestation.
The most accurate way to diagnose IUGR is via ultrasound. Even if a mother is sure of her dates, an ultrasound can provide a comprehensive overview of the baby’s development and size. As the pregnancy progresses, the baby’s growth can be compared with previous scans to compare its increase in size.
Growth parameters that are checked include:
The baby’s head circumference
The length of the femur – the long bone that runs from the hip to the knee
The abdominal girth measurement
The blood-flow from the placenta through the umbilical cord
Treatment/Management for IUGR
Treatment is usually based on close monitoring of the baby to ensure that it’s not being compromised, via regular scans, foetal monitoring, antenatal check-ups for the mother and regular weighing.
If the medical and obstetric team assess that the baby would be better off being delivered, rather than remaining in the womb, labour may be induced or a caesarean section delivery performed. Obviously, weighing up the costs vs. benefits needs to be done carefully; premature babies come with their own unique set of complications.
Bed rest, referral to a specialist dietician, minimising stress and aiming for a calm, enjoyable pregnancy all help. Unfortunately there is no guarantee that these strategies will correct the situation. Sometimes, the only solution is to nurture a mother and her baby along until they are at a reasonably safe gestational stage; if the baby is viable, a caesarean section delivery is organised. Babies with IUGR stress easily, which is why a normal delivery is not always possible.
Risks to the Baby of Having IUGR
More likely to become distressed during labour and not being able to breathe independently
May have trouble maintaining its own temperature due to immaturity and low fat stores
Can be very hungry, even in the early days following delivery
May have problems with low blood sugar and require monitoring in a special care unit
Babies with IUGR are more prone to infections and becoming unwell, simply because they are less robust than normal sized babies
Here’s the Good News
As long as the baby does not have an abnormality and, apart from being born small, is otherwise normal and healthy, the odds are high that they will do very well. Frequent feeding, monitoring of intake and regular weighing all help to support IUGR babies towards a healthy weight gain.
Ideally, breastfeeding should be established as soon after birth as possible. Colostrum is the perfect food for newborn babies as it is high in kilojoules, fat and antibodies to fight infection. Mothers of babies with IUGR need to accept that it can take weeks of frequent feeding, offering the breast on “demand” and not expecting to have any regular feeding regime, before their small baby catches up.
Regular attendance at the child health centre or GP is important. Babies with IUGR need to be weighed and measured, then plotted on their percentile (growth) charts. Babies who drop down on their growth line need to be referred for specialist paediatric monitoring.