Background Sepsis is one of the most important complications in preterm infants.

For this reason, many such infants receive antibiotics during their hospital stay.

However, early antibiotic therapy has also been associated with adverse outcome.

It is yet largely unclear if the time of onset of antibiotic therapy influences the outcome.

We here investigated whether the timing of initiation of antibiotic therapy plays a role in the association between antibiotic exposure and short-term outcome.

Methods Retrospective analysis of data from 1762 very low birthweight infants born in a German neonatal intensive care unit (NICU) between January 2004 and December 2021.