Most babies screened will not have any of the conditions but, for the small numbers who are discovered to have one, the benefits of screening at the earliest possible opportunity are enormous.
Early treatment can greatly improve a baby’s health and may prevent severe disability.
What conditions are newborn babies screened for?
In the UK, all babies are screened for phenylketonuria, congenital hypothyroidism and cystic fibrosis.
In England, babies are also screened for sickle cell diseases and medium-chain acyl-CoA dehydrogenase deficiency (MCADD).
If you want to know which conditions are screened for in your area, please ask your midwife.
Phenylketonuria is an inherited condition – in other words, it runs in families. In the UK, around 80 babies are born each year with the condition.
Babies born with phenylketonuria cannot process a substance in their food called phenylalanine, so this substance builds up in the body’s tissues. Phenylalanine is usually broken down by the action of the enzyme phenylalanine hydroxylase. But in phenylketonuria, the enzyme doesn't work properly and the body can’t break down phenylalanine.
If left untreated, this can seriously affect the development of a baby’s brain and can lead to severe mental disability.
Screening means that babies with the condition can be treated early through a special diet, which will prevent severe disability and allow them to lead a normal life.
About congenital hypothyroidism
Congenital hypothyroidism is a condition where, for a number of reasons, the thyroid gland doesn’t work when a baby is born or fails to make enough thyroxine, the thyroid hormone. Without this hormone, babies do not grow properly and can develop serious, permanent physical and mental disability.
In the UK, around 275 babies are born each year with congenital hypothyroidism. Screening means that babies with congenital hypothyroidism can be treated with thyroxine tablets, which will allow them to develop normally.
About cystic fibrosis
Cystic fibrosis affects around 240 babies born each year in the UK. The condition affects the internal organs, especially the lungs and digestive organs, by clogging them with thick, sticky mucus. This makes chest infections common and causes digestive problems.
The condition is caused by a faulty gene. Over two million people in the UK, around one in 25 people, are carriers for this gene. If two carriers have a child, the baby has a one in four chance of having cystic fibrosis.
If a baby is found to have cystic fibrosis they can be treated early with a high energy diet, medicines and physiotherapy.
The screening test also picks up a small number of cystic fibrosis, and these results are also reported to parents.
About sickle cell disorders
Sickle cell disease is the most common inherited condition in the UK. It is a blood disorder that most often affects children of Afro-Caribbean descent, but can affect children from other ethnic backgrounds too.
A child with sickle cell disease has red blood cells that can change shape and become stuck in small blood vessels. This can cause pain, and can damage the baby’s body.
The condition also causes anaemia. Symptoms include tiredness and breathlessness, as a result of a reduced ability to carry oxygen around the body. Serious infections and death may occur.
If detected early, treatment including immunisations and antibiotics can be started, which will help to prevent serious illness and allow a child to lead a healthier life.
MCADD is a rare, inherited condition in which the body has problems breaking down fats to make energy. This is because a vital enzyme is missing. In babies with MCADD, problems may occur when a baby misses food, or is ill and/or sick and needs to break down fat quickly. This can result in serious illness or death.
Once diagnosed, it’s possible to prevent serious illness by teaching parents to make sure their baby eats regularly and to pay special attention to what they eat. Children with MCADD therefore usually lead normal, healthy lives.
In the UK, around 66 babies are born each year with MCADD.
How is screening done?
A small sample of blood is taken from your baby’s heel (known as the heel prick test) around a week after the birth. This is done using an automated device especially designed for newborn babies.
The heel prick may be uncomfortable and your baby may cry. You can help by making your baby warm and comfortable, talking and maintaining eye contact and by feeding or cuddling your baby.
The midwife collects spots of blood on a screening card. After the test is completed, any excess blood from the baby’s heel is wiped away and gentle pressure applied using a cotton wool ball to prevent excessive bleeding and bruising.
Are repeat samples ever needed?
Occasionally you may be contacted for a second heel prick sample. This may be because not enough blood was collected, the result was unclear, or your baby was born early or had a blood transfusion.
Your midwife will explain the reason to you. It is important that a repeat test (if needed) is done so that all the tests are completed. Usually the repeat results are normal.
What happens next?
Most babies will have normal results indicating that they are not thought to have any of the conditions.
In most areas, a health professional will let parents know the results and record them in a baby’s personal child health record. If you haven‘t received this information, you should ask your health visitor or GP.
Results are usually available by the time of your baby’s 6-8 week health check.
A negative screening result suggests that it is unlikely that your child has any of the screened conditions.
A positive screening result suggests that it is more likely that your child has one of the screened conditions. Further diagnostic tests will be needed to confirm whether your baby is affected.
Some babies are found to be carriers (of either cystic fibrosis or sickle cell disease). Parents are usually told by the time their child is 6-8 weeks old.
What happens if the results are positive?
If your baby is thought to have one of the conditions, you will be contacted and given an appointment with a specialist.
Further diagnostic tests will be made to confirm the presence or absence of the condition.
In your area
Your midwife should give you a copy of the national pre-screening leaflet when you are about 30 weeks pregnant, and will be able to confirm which conditions are screened for in your area.