Jakkaew 2013.

Methods	RCT, 1 hospital in Thailand (Chiang Mai University).
Participants	50 women randomised after CS; > 80% were non‐elective CS, > 50% of the participants were having a 1ary CS; > 80% under regional anaesthesia. Participants included both nulliparas and multiparas; mean of age 31.2 ± 6.33 and 29.48 ± 5.91 years in control and gum group. Inclusion criterion: "at least 15 years of age". Exclusion criteria: hysterectomy, "surgical management of severe postpartum haemorrhage, perioperative hyperalimentation, previous bowel surgery (except for appendectomy), bowel obstruction, history of inflammatory bowel diseases, recent chemotherapy (less than 1 week), previous abdominal or pelvic radiation, postoperative endotracheal or naso/orotracheal intubation, and postoperative admission to intensive care unit".
Interventions	Intervention group (N = 25): "Chew two tablets of artificial fresh mint flavoured sugarless gum (LotteXylitol®, Thai Lotte Co., Ltd., Chonburi, Thailand) for 30 minutes four times a day (morning, noon, evening, and before bed time) starting since the regain of consciousness and normal vital sign until the first passage of flatus (total chewing time = 120 minutes/day). For those who were allowed to receive diet but had not had first passage of flatus, they were asked to continue gum chewing for 30 minutes before each meal and at bedtime until the first passage of flatus. To promote compliance, the gums were provided to participants by ward nurses at specific times". Control group (N = 25): "conventional feeding protocol, i.e. not given anything by mouth after surgery until at least 2 of the following signs": bowel sound, feeling of hunger, passage of flatus or defecation. "Then sips of water were allowed. Subsequently, the feeding schedule proceeded to liquid diet for the next meal. Soft diet was given on the next day given good tolerance to the liquid diet. Once the passage of flatus occurred, diet was advanced to regular diet."
Outcomes	Time of the first passage of flatus (in median), duration of hospital stay (in median), rate of participants with symptoms and signs of gastrointestinal disturbances (nausea, abdominal cramping, abdominal distension, rate of vomiting)*. Additional outcomes: time to the first meal; level of feeding satisfaction; time to the first regular diet; tolerance to the first meal; rate of postoperative complications such as fever, pneumonia, wound infection and lung atelectasis.
Notes	Due to the form the authors used to present the results (median and ranges), we could not use the time to passage of flatus or duration of hospital stay in our meta‐analyses. *The number of women with vomiting episodes is reported for day 1 and day 2 (as N, %), but we do not know if it was the same woman or not. We wrote to the study authors for additional information and obtained no answer. Therefore, this study was not included in any of our meta‐analyses. IRCT NCT01131416.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"The random sequence was generated by a computer‐based program. Randomization was stratified according to the type of anaesthesia (regional anaesthesia and general anaesthesia)."
Allocation concealment (selection bias)	Low risk	"Participants were randomly assigned into two groups by central telephone assignment."
Blinding of participants and personnel (performance bias) All outcomes	High risk	The nature of intervention did not allow blinding of participants and personnel.
Blinding of outcome assessment (detection bias) Subjective outcomes	High risk	Participants were unable to be adequately blinded in relation to passage of flatus.
Blinding of outcome assessment (detection bias) Objective outcomes	Unclear risk	"The symptoms and signs of gastrointestinal disturbance were evaluated daily by the outcome assessor who was blinded to the study allocation." No information on blinding of outcome assessors for duration of hospital stay.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	"No participant was excluded from analysis." However the sample size reported in the paper (50) is only half of the size proposed in the protocol (100). We contacted the study authors for more details but they did not reply.
Selective reporting (reporting bias)	High risk	Passage of stools, rate of ileus and woman's satisfaction were described as outcomes in the protocol but not reported in the paper.
Other bias	High risk	In the protocol, the sample size was described as 100 participants (50 in each group); the publication describes only 50 participants (25 in each group). It is possible that the study was ended before the proposed time.