Kettle 2002.

Methods	RCT. Factorial ‐ 2 x 2 design.
Participants	Setting: UK district general hospital. 1542 women needing perineal repair following delivery (second‐degree tears and episiotomies included). Method of delivery: spontaneous vaginal deliveries. Parity: primiparous and multiparous. Mean age: continuous (group A) 27.2 years; interrupted (group B) 27.2 years. Operators: midwives (N = 150), 29 women sutured by doctor.
Interventions	Method of repair: described as below. Women divided into 2 groups. Group A (N = 771) vaginal trauma, perineal muscle and skin repaired with a continuous non‐locking suture technique. 50% were repaired with undyed Vicryl Rapide 2/0 on a 35‐mm tapercut needle and 50% were repaired with undyed standard Vicryl on a 35‐mm tapercut needle. Group B (N = 771) vaginal trauma repaired with a locking continuous stitch; perineal muscle and skin sutured using the interrupted method. 50% were repaired with undyed Vicryl Rapide 2/0 on a 35‐mm tapercut needle and 50% were repaired with undyed standard Vicryl on a 35‐mm tapercut needle.
Outcomes	Included in analysis: short‐term pain at days 2 and 10; pain when walking, sitting, passing urine, opening bowels at 10 days; analgesia at day 10; long‐term pain at 3 and 12 months; dyspareunia at 3 and 12 months; removal of suture material at 3 months; Additional analyses in Kettle 2002.
Notes	Method of repair: described. Training period: described Concealed interim analysis after 400 women entered the trial. Ethics Committee Approval. 1 envelope unaccounted for.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Allocated randomly by remote clinical trials unit. Random permuted block design.
Allocation concealment (selection bias)	Low risk	Concealed treatment allocation ‐ serially numbered, sealed opaque envelopes, (envelopes contained 2 packets of masked suture material and instructions for method of repair on different coloured cards).
Blinding (performance bias and detection bias) Clinical staff	High risk	Differences in suture techniques.
Blinding (performance bias and detection bias) Women	High risk	Women may have been aware of suturing technique.
Blinding (performance bias and detection bias) Outcome assessors	High risk	Fully blind assessment was not possible owing to obvious differences in suture techniques.
Incomplete outcome data (attrition bias) All outcomes	Low risk	1542 women randomised and primary analysis was by ITT. High response rate at day 10 and at 3 and 12 months' follow‐up (96.7% response rate at 3 months and 90% at 12 months).
Selective reporting (reporting bias)	Unclear risk	Not apparent.
Other bias	Unclear risk	No baseline imbalance apparent. There were some protocol deviations (less experienced staff were more likely to use interrupted sutures).