Factors influencing delayed onset of lactation: a systematic review and meta-analysis

Delayed onset of lactogenesis (DOL), defined as the absence of breast fullness or milk coming in beyond 72 h postpartum, may impair breastfeeding success. Reliable estimates of its incidence and associated factors are needed to guide clinical support. Following PRISMA 2020, we systematically searched English and Chinese databases from inception to 30 April 2025 for prospective observational studies of factors associated with DOL among women initiating breastfeeding. Two reviewers independently screened studies and extracted data. DOL incidence was pooled using logit-transformed proportions and a Paule–Mandel random-effects model, with subgroup analysis by country. Odds ratios (ORs) for associated factors were synthesised using fixed- or random-effects models according to between-study heterogeneity. Across 48 prospective studies ( n = 39,388), the pooled incidence of DOL was 30.3% (95% CI 26.9%–33.9%; I² = 96.8%). Incidence differed across country subgroups ( P < 0.001). Among factors evaluated in at least three studies, higher odds of DOL were associated with maternal age ≥ 35 years (OR 2.31), primiparity (OR 2.04), cesarean section (OR 1.51), anxiety (OR 2.83), depression (OR 2.16), gestational hypertension (OR 3.05), and gestational diabetes mellitus (OR 1.73). Higher breastfeeding frequency (OR 0.85 per additional feed), previous breastfeeding experience (OR 0.27), and prenatal breastfeeding education (OR 0.63) were associated with lower odds. DOL occurred in approximately three in ten participants in the included studies. The evidence supports attention to maternal obstetric and metabolic conditions, psychological well-being, and modifiable breastfeeding support practices, while associations based on sparse evidence require confirmation.