Hurtado 2017.

Study characteristics
Methods	Design: randomised controlled trial Setting: Spain
Participants	Number of participants: (N = 625) Number of dropouts (per group if available): A 164, B 170 Inclusion criteria: healthy women between 18 and 45 years with development of normal pregnancy, childbirth took place 1– 6 days before recruitment, birth between 37 and 42 weeks of gestation, women who had received preventive antibiotic treatment between 48 hours before and 48 hours after childbirth (1 dose was sufficient for inclusion regardless of the type of antibiotic), and women with firm intention to breastfeed their children for at least 16 weeks Exclusion criteria: mammary pathologies or children’s pathologies that hinder or preclude breastfeeding and low expectation of adherence to the study protocol
Interventions	Intervention A: (N = 303) probiotics: 1 capsule/day containing L. fermentum 3 x 109 CFU Control B: (N = 322) placebo: 1 placebo capsule/day containing maltodextrin Duration of treatment: 16 weeks Duration of follow‐up: 16 weeks postpartum
Outcomes	Incidence of clinical mastitis during the first 4 months of breastfeeding. Mastitis defined as at least 2 out of the 3 breast symptoms (pain, redness, and lump) and at least 1 of fever or flu‐like symptoms (shivering, hot sweats, or aches) Secondary outcomes: microbiota of breast milk at the end of intervention and in mastitis events, monthly questionnaire on evaluation of breast pain, and inflammatory markers in breast milk at the end of intervention and in mastitis events
Notes	Dates of study: August 2013 to July 2015 Funding sources: “This study was financed by the Andalusian Government and co‐financed by the European Regional Development Fund under the Andalusia’s 2007–2013 Global Innovation‐Technology‐Enterprise Grant”. Declarations of interest: “JAM‐L, MPD‐R. MO, JF, OB, CR, ADV, and AS are workers of Biosearch Life, owner of the patent of Lactobacillus fermentum CECT5716". Contacted author 16th July 2020 to query the numbers of women withdrawing from the trial because it appeared that some women with mastitis were not included in the mastitis incidence analysis; email address of correspondence author was no longer active and we could not find contact details for the other authors.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“randomization generated by a computer program”
Allocation concealment (selection bias)	Unclear risk	Not reported
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Participants and caregivers blinded
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Investigators and outcome assessors blinded
Incomplete outcome data (attrition bias) All outcomes	High risk	High attrition in both groups, but not differential (164/303 and 170/322), mainly due to “voluntary resignation” (56/303 and 54/322) and other reasons related to breastfeeding difficulties (70/303 and 76/322 women decided to stop breastfeeding due to perception of insufficient milk or mastitis, 5/303 and 7/322 due to gastrointestinal problems in infants or maternal rash) Some women appeared to have discontinued the intervention due to developing mastitis; these women were not included in the four‐month analysis. Analysis was per‐protocol.
Selective reporting (reporting bias)	High risk	Not all outcomes were reported in full.
Other bias	Unclear risk	Some of the authors work for the patent owner of the intervention (JAM‐L, MPD‐R, MO, JF, OB, CR, ADV, and AS). It was not clear if this had any influence on the results.