Skip to main content

Table 1 Power calculations with n = 904** in each arm

From: COSMOS: COmparing Standard Maternity care with One-to-one midwifery Support: a randomised controlled trial

Outcome Standard care Caseload Power to detect specified difference
  % %  
Birth by caesarean section 19 14 80
Instrumental vaginal birth 10.6 6.6 84
Epidural analgesia 18 13 82
Intact perineum or unsutured laceration (increase)* 41.2 48.2 84
Intact perineum or unsutured laceration (decrease)* 41.2 34.2 86
3rd or 4th degree laceration* (would not miss this difference) 1.7 3.4 57
Induction of labour 27 21 84
Augmentation of labour 19 14 80
Exclusive breastfeeding at 6 months 8 12 79
Any breastfeeding at 6 months 53 63 99
Postnatal depression at 8 weeks 15 10 88
Postnatal depression at 6 months 15 10 88
Smoking at time of birth 15 10 88
  1. *These estimations exclude caesarean births
  2. ** Allows for loss to follow-up