There are several indications to use a<unk>  to aid delivery: * Maternal exhaustion * Prolonged second stage of labor * Foetal distress in the second stage of labor, generally indicated by changes in the foetal heart-rate (usually measured on a CTG) * Maternal illness where prolonged "bearing down" or pushing efforts would be risky (e.g. cardiac conditions, blood pressure, aneurysm, glaucoma). If these conditions are known about before the birth, or are severe, then an elective caesarean section may be performed.
Vacuum extraction
Culture conversion
Terminal cleaning
Freeze spray
Global distillation
Sterilization 
Agar dilution
Decontamination