Table 2 Randomised controlled trials comparing various filling volumes.

Lead author	Year	n	Standard filling volume (SF)	Greater filling volume (GF)	Significant results
Levy R 18	2004	203	30 ml	80 ml	Cervical dilatation ≥ 3 cm to cervical ripening (%)SF: 52.4GF: 76.0	p < 0.001
					Vaginal delivery rate in 24 h in nullipara (%)SF: 49.0GF: 71.4	p < 0.05
					Oxytocin augmentation in nullipara (%)SF: 90.4GF: 69.3	p < 0.05
Kashanian M 19	2009	270	30 ml with traction	80 ml without traction	Bishop score ≥ 9 (%)SF: 38.9GF: 83.3	p < 0.001
					Vaginal deliveries (%)SF: 83.3GF: 90.0	p < 0.001
Delaney S 17	2010	192	30 ml	60 ml	Vaginal delivery rate in 24 h (%)SF: 14.0GF: 26.0	p < 0.04
					Cervical dilatation at balloon expulsionSF: 3 cmGF: 4 cm	p < 0.01