Roberts 1998.

Methods	Double‐blind randomised controlled trial.
Participants	39 lactating, postpartum women with breast engorgement recruited from postnatal wards at Royal Darwin Hospital and Darwin Private Hospital, Australia. Breast engorgement defined as hard, warm, painful breasts with difficulty feeding. Exclusion criteria: Aboriginal women (tend to have less breast engorgement), women allergic to roses or the cabbage family of plants. Majority were multiparas with prior breastfeeding experience, who reported the appearance of engorgement symptoms on day 3 postpartum. Significantly more primiparas were in the intervention group.
Interventions	Intervention group (21 women): base cream with 1% cabbage leaf extract (according to British Pharmacopoeia formulation). Control group (18 women): base/placebo cream only. Rosewater added to both creams to camouflage residual odour of cabbage. 1 tube of cream was applied liberally to both breasts and left on for 2 hours. The 2‐hour period was chosen since cabbage leaves had been shown to act within this period of time, and it could be done within the inter‐feeding period. Mothers were asked to refrain from showers, analgesia and feeding the baby during this period.
Outcomes	Pain, using Bourbonnais pain scale (a visual analogue scale). Chest circumference, using plastic tape measure. Degree of hardness, using Roberts durometer. Degree of engorgement, using Hill and Humenick Breast Engorgement Scale. Outcomes measured at baseline, 2 hours after application of cream and following subsequent breastfeed.
Notes	Authors were contacted to clarify method of cream application, i.e. to elucidate whether application method (e.g. massage) contributed to treatment effect. According to authors ˝the cream was lightly rubbed in, not massaged, just enough pressure to have the cream absorbed˝. Authors were also contacted to confirm that results shown in Table 3 refer to post‐test measurements (not stated in manuscript), and to check whether there were any significant differences between experimental and control groups for pretest values (given as a combined measure, in Table 4). Precise data on the latter could not be provided, since Australian regulations require data be kept for 5 years only post‐publication, but according to trial authors no differences were detected. The authors report that breastfeeding had a better effect than application of cream in relieving discomfort and decreasing tissue hardness.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	˝Randomised assignment list generated using coin toss.˝
Allocation concealment (selection bias)	Unclear risk	˝Group assignments were placed in sealed envelopes˝ but type of envelope not stated (transparent or opaque).
Blinding (performance bias and detection bias) Women	Low risk	Women did not know which cream they were using as the creams were identical in colour and odour.
Blinding (performance bias and detection bias) Clinical staff	Low risk	The same midwife applied the cream and performed the measurements. The midwife was however blinded to the groups the women were in.
Blinding of outcome assessment (detection bias)	Low risk	The midwife who assessed the outcomes was blinded to the allocations.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No loss of data.
Selective reporting (reporting bias)	Unclear risk	All outcomes were reported but in a form that could not be easily interpreted. Pre‐test measurements for each outcome were given as a single value, i.e. for both groups combined, so change in outcome measures could not be accurately calculated.
Other bias	High risk	A significant imbalance in primiparas at baseline (P = 0.047) may have been due to chance but may also have been due to possible allocation concealment bias or compromised blinding.