Ingelman‐Sundberg 1953.

Methods	Quasi‐randomised trial. Allocation by folder numbers.
Participants	45 women with pronounced signs of engorgement during the second to the 4th day postpartum. Women were located on a private hospital ward in Stockholm, Sweden.
Interventions	Intervention group (20 participants): oxytocin 2.5 IU given subcutaneously daily to women until breasts became soft. Control group (25 participants): a corresponding amount of physiological saline was given similarly. In both groups the baby was allowed to breastfeed from the first day after delivery.
Outcomes	Amount of breast milk produced. Duration of treatment before the engorgement disappeared.
Notes	There were only limited data we were able to use in data tables. The authors state that the baby was allowed to suckle from the first day after delivery and the volume of milk was measured. The results state that the daily amount of milk produced was the same in both groups, although it was not clear how the amount of milk produced was measured.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Odd or even folder numbers.
Allocation concealment (selection bias)	High risk	There was no allocation concealment. Women were allocated into different groups based on their hospital records.
Blinding (performance bias and detection bias) Women	Low risk	"It was concealed from both patient and doctor whether oxytocin or saline was being used."
Blinding (performance bias and detection bias) Clinical staff	Low risk	"It was concealed from both patient and doctor whether oxytocin or saline was being used."
Blinding of outcome assessment (detection bias)	Unclear risk	The article does not mention blinding of outcome assessors.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	The study does not mention how incomplete outcome data were addressed.
Selective reporting (reporting bias)	Unclear risk	The authors report their outcomes in percentages not in numbers out of the totals; which makes it difficult to determine the denominators.
Other bias	Low risk	No other bias identified.