Greek to English Medical Medical (general) Neonatal infections

Here I am stumped by an abbreviation again, this time from a set of slides, so there's very little context. It's from a list of possible risk factors for fungal infections in neonates.

Χειρουργικές επεμβάσεις (κυρίως στο ΓΕΣ)

The abbreviation does not appear anywhere else in the source. As usual, my mind goes blank when confronted with something like this.

Any ideas?