Erasmus MC in Rotterdam began a DNA test Monday for premature babies in intensive care, NU.nl reports. The test identifies a genetic mutation that can cause permanent deafness from a common antibiotic.

Premature infants nearly always receive antibiotics. Doctors often cannot tell right away if the babies have an infection. The standard drug is gentamicin, which works against many infections. But one in every 300 to 400 children carries a genetic mutation. That mutation can cause lasting hearing damage if the child receives gentamicin.

The new test uses a cheek swab taken right after birth. Results come back within an hour. Doctors can then switch to a different antibiotic if needed.

Ron van Schaik is a professor of pharmacogenetics and a clinical chemist at Erasmus MC. He said it is not wise to give the alternative drug to every premature baby. Doing so raises the risk of antibiotic resistance.

The test was approved after research in England showed it works. Other Dutch hospitals may adopt the method later. “The challenge lies in the logistics, because the test result must be known within an hour,” van Schaik told NU.nl.

The mutation is passed down through the mother. When a baby has the sensitivity to gentamicin, the hospital also notifies the family. That includes the mother, her sisters and their children.