The Metabolic disorders
There are four main metabolic disorders that are commonly tested for with newborn screening tests:
Cystic fibrosis
Galactosaemia
Congenital hypothyroidism
Phenylketonuria
Cystic fibrosis
Cystic fibrosis (CF) is a genetically inherited disorder that causes a baby's intestines and lungs to produce very thick, tenacious mucus as well as affecting the functioning of their pancreas. The mucus in the lungs is associated with inflammation and can make the baby susceptible to frequent chest infections, requiring antibiotics. The mucus in the intestines creates problems with the baby absorbing and digesting food and slows the passing of bowel motions and the baby's pancreas is unable to produce sufficient enzymes to adequately digest food.
Babies with CF may eat well, but gain little weight and at times have a cough from a very young age. They also may not pass their first bowel motion as expected after birth within the first 24 hours (called meconium ileus).
Cystic fibrosis affects about 1 in 2,500 babies (0.0004%) in white Caucasian populations, but is less common in Asian and black African races. The disorder can be carried by healthy parents and passed to their baby if both parents carry the gene for CF. When both parents are healthy but carry the CF gene, they have a 25% chance of having a baby who has CF, a 50% chance of having a baby who is healthy but is a carrier of the CF gene (like themselves) and a 25% chance of having a baby who is neither a carrier nor a sufferer of CF.
It is possible for parents with a family history of CF to be tested to see if they carry the CF gene. This can give them an opportunity to seek genetic counselling prior to conceiving a baby or to consider genetic tests for their baby early in the pregnancy to detect CF.
CF used to be tested for by taking a sample of the baby's first poo (meconium). However, this test could be very unreliable.