Around 540 patients - mothers and babies - have been notified by hospitals that there is a small chance their baby may have been incorrectly blood grouped at birth, due to a mislabelling of a blood test kit for newborns.

The Health Service Executive says there are no immediate safety concerns and the risk of a baby's blood test group being incorrect is extremely low.

The five maternity hospitals affected are the Rotunda Hospital in Dublin, Cavan General, Sligo General, Limerick and Galway.

Most of the cases are at the Rotunda, one of the biggest hospitals in the country.

The hospitals began contacting affected mothers on Monday and letters have been sent to anyone potentially affected by the manufacturing error.

GPs are also being notified.

There are four groups of patients potentially affected:

- Mothers who may have required an anti-D injection but did not receive it (30 cases).

- Mothers who may have received anti-D when they did not need it (220 cases).

- Babies who received a red blood cell transfusion when they may not have needed it (12 cases).

- And babies whose blood group result may have been reported incorrectly (278 cases).

The test kit involved is the ORTHO BioVue System Cassette.

The HSE says it was recently notified by Ortho Clinical Diagnostics, a Johnson & Johnson company, that a small number of the testing kits supplied worldwide have been incorrectly labelled.

The HSE says that all hospitals have completed an inspection of the remaining kits in stock and have removed any potentially affected batches.

It says that all patients, including babies, will always have a repeat blood group test when being admitted to any hospital or in pregnancy.

However, if any mothers would like their babies to be re-checked now, this will be done.