All babies in England are to be screened for sickle cell blood disorders within two weeks of birth.
The baby's heel is pricked to collect some small drops of blood
The check, carried out as part of the standard "heel-prick test" that looks for other health problems, spots both the full-blown disease and carriers.
Sickle cell is a condition that affects the normal oxygen carrying capacity of red blood cells and ranges in severity.
In England, it affects about 12,500 people and about 240,000 are carriers of the faulty genes that cause it.
The screening, which has been introduced over recent years, is expected to identify more than 300 babies a year in England who would otherwise be at very high risk of severe complications and, in some cases, death if the correct treatment is not administered, experts estimate.
The heel prick test, which also checks for a range of other diseases such as cystic fibrosis, is carried out by midwives or health visitors in the first week or two after the birth.
Heel prick test
The test involves pricking the baby's heel to collect some small drops of blood.
In Britain, sickle cell is most common in people of African and Caribbean descent. However, it can affect anyone.
Racial diversity and mixed race marriages also means more people could be carriers but not realise that they are.
Allison Streetly, director of the NHS Sickle Cell & Thalassaemia Screening Programme, said screening was crucial to spot those at risk.
She explained: "It is no longer possible to assume who may or may not be affected."
All pregnant women in England should also be offered a blood test in early pregnancy to check whether they carry a gene for sickle cell anaemia or a similar blood disorder called thalassaemia.
Where a woman is a genetic carrier, the baby's father is also offered testing. If both parents are carriers, there is a one in four chance with each pregnancy that the baby will have the disorder.
At-risk couples will be offered a range of counselling and diagnostic tests for the baby.
Such antenatal screening has been rolled out in most high prevalence areas. It is hoped full coverage throughout England will be achieved by summer 2007.
Dr John Sentamu, Archbishop of York and chair of the NHS Sickle Cell & Thalassaemia Screening steering group, said he was delighted to see the investment in screening, but said investment in care was now needed.
A spokeswoman from the Sickle Cell Society said couples should also consider screening before trying for a baby.