Robson 1990.

Methods	Randomised controlled trial.
Participants	88 breastfeeding mothers with "varying degrees" of breast engorgement, all mothers had a caesarean section. Exclusion criteria: oriental ethnic background (it is not clear how many women were excluded for this reason).
Interventions	Intervention group: breast‐shaped cold packs worn 15‐20 min after 2 consecutive feeds. Control group: routine care which encouraged the use of supportive bras, warm compresses. manual expression/pumping of breasts, demand feeding and night time feeding, with intervals between feeds not being longer than 5 hours and each feed taking 30 min to 1 hour.
Outcomes	Pre‐ versus post‐test pain scores. Scores were not reported in a way in which we were able to include them in data tables. We have briefly summarised the results in the text of the review. Transfer of milk. Degree of engorgement.
Notes	This study is at high risk of bias. Women in the intervention group who were most distressed were moved into the control group, and those in the control group who wanted packs were moved to the intervention group.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Table of random numbers generated but randomisation sequence was not observed. 8/88 women were not allocated according to randomisation schedule but according to preferred treatment arm.
Allocation concealment (selection bias)	Unclear risk	The authors did not make mention of allocation concealment.
Blinding (performance bias and detection bias) Women	High risk	The nature of the study did not allow blinding of women.
Blinding (performance bias and detection bias) Clinical staff	High risk	The nature of the study did not allow blinding of clinical staff.
Blinding of outcome assessment (detection bias)	High risk	A record of each participant was kept so that data could be analysed without their results.
Incomplete outcome data (attrition bias) All outcomes	High risk	There were serious protocol deviations and no ITT analysis.
Selective reporting (reporting bias)	Low risk	The authors reported on all pre‐specified outcomes.
Other bias	High risk	There was considerable baseline imbalance. Women in the control groups had much lower pretest pain scores. This may be due to the fact that 3 women with the most severe symptoms were moved out of the control group and into the intervention group. There was no ITT analysis.

BP: blood pressure
 ITT: intention‐to‐treat
 IU: international unit(s)
 min: minutes
 SBES: subjective breast engorgement scale