Summary of findings 2. Antibiotics compared to usual care or placebo for preventing mastitis after childbirth.

Antibiotics compared to usual care or placebo for preventing mastitis after childbirth
Patient or population: postpartum breastfeeding women Setting: obstetric outpatient clinic Intervention: antibiotics Comparison: usual care or placebo
Outcomes	Anticipated absolute effects* (95% CI)		Relative effect (95% CI)	№ of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Risk with usual care or placebo	Risk with antibiotics
Incidence of mastitis within 6 months postpartum	Study population		RR 0.37 (0.10 to 1.34)	429 (3 RCTs)	⊕⊕⊝⊝ LOW 1
	37 per 1000	14 per 1000 (4 to 49)
Recurrence of mastitis within 12 months postpartum	Not reported
Breast abscess within 6 months postpartum	Not reported
Nipple damage within 6 months postpartum	Not reported
Duration of any breastfeeding	Not reported
Breast pain	Not reported
Number of women with adverse effects	Not reported
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: Confidence interval; RR: Risk ratio; OR: Odds ratio;
GRADE Working Group grades of evidence High certainty: We are very confident that the true effect lies close to that of the estimate of the effect Moderate certainty: We are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different Low certainty: Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect Very low certainty: We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect

¹ Downgraded two levels due to imprecision: low event rate and wide 95% CIs indicating the true effect may be either appreciable benefit or harm