CUH Logo

Mobile menu open

Positive Direct Antibody Test (DAT)

Patient information A-Z

This leaflet explains what a direct antibody test DAT is and what to expect if it is positive for your newborn baby.

What is DAT?

DAT tests for evidence of a reaction between the mother’s and baby’s blood groups. If your baby’s DAT is positive, there is a risk that he/she could develop anaemia (low number of red blood cells) and/or jaundice (yellow colour to the skin). However, only a small number of DAT positive babies will develop these problems. Babies who are not DAT positive can still develop anaemia and jaundice. A positive DAT alerts us to look out for any signs of anaemia and jaundice. It does not necessarily mean that your baby will need treatment.

Please note: Pregnant women whose blood group is Rhesus negative may receive injections to prevent them producing antibodies against their baby’s blood. Sometimes this injection can cause the test to be positive. Babies who are DAT positive for this reason do not usually develop anaemia or jaundice.

What is jaundice?

Jaundice is a yellow colour to the skin. It is caused by the build-up of a pigment called bilirubin in the skin. Bilirubin is released from broken down red blood cells. A mild degree of jaundice is very common in newborn babies and is not usually a problem.

However, babies who are DAT positive may have higher levels of jaundice. High levels of jaundice need to be treated, usually by phototherapy which involves exposing the baby to a light source.

What is anaemia?

Anaemia means that there are lower numbers of red blood cells than usual. Anaemia can occur in DAT positive babies because their red blood cells are broken down by their mother’s antibodies.

The anaemia may not be present at birth, but can develop over the first few weeks or months of life.

What will happen if my baby’s DAT is positive?

In the first few days your baby will be examined by a member of the neonatal team. Blood tests will be taken to look for jaundice and anaemia. High jaundice levels will be treated with phototherapy.

How should I monitor my baby at home?

If your baby is at higher risk of developing anaemia, we will arrange for mother and baby to return to the hospital clinic for review and further blood tests.

Whether or not you have been given a follow up appointment, symptoms to monitor for at home include:

  • increasing jaundice
  • excessive sleepiness
  • poor feeding
  • fast breathing or difficulty breathing
  • baby appears pale

If you are worried, contact your midwife or General Practitioner (GP).

Will there be any long-term problems?

Most babies do not have any long-term problems. The mother’s antibodies which have caused the DAT to be positive reduce in number and are usually gone from the baby’s blood by two to three months of age. Babies also start to produce new red blood cells naturally by this age.

Contacts/further information

If you need further advice or information, please speak to your midwife or GP.

We are smoke-free

Smoking is not allowed anywhere on the hospital campus. For advice and support in quitting, contact your GP or the free NHS stop smoking helpline on 0800 169 0 169.

Other formats

Help accessing this information in other formats is available. To find out more about the services we provide, please visit our patient information help page (see link below) or telephone 01223 256998.

Contact us

Cambridge University Hospitals
NHS Foundation Trust
Hills Road, Cambridge

Telephone +44 (0)1223 245151