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Validity and public health implications of maternal perception of the onset of lactation: an international analytical overview.

The main objective of this analytical overview is to assess the validity of maternal perception of the onset of lactation (OL) as an indicator of lactogenesis stage II (LS-II). Prospective studies that assessed OL and/or LS-II [based on test-weighing milk volume (MV) and/or breast milk biomarkers (BMB)] were identified. OL is a clearly defined and easily identified event across cultures, with the overwhelming majority of women being able to report when they experience it. Mean OL ranges from 50 to 73 h postpartum across studies and from 1 to 148 h postpartum within studies. The wide range detected within samples is fully consistent with the wide within sample LS-II variability as determined by BMB or MV. Studies have identified similar risk factors for delayed LS-II, such as labor and delivery stress, primiparity and insulin-dependent diabetes mellitus, regardless of marker used (i.e., OL, MV or BMB). The correlation between OL and MV (r = -0.60) is of similar magnitude to that between OL and BMB (r = 0.50) and that between BMB and MV (r = 0.47-0.69). In conclusion, OL is a valid clinical indicator of LS-II. This has public health relevance because studies have identified delayed OL (i.e., >72 h postpartum) as a risk factor for shorter breastfeeding duration and for greater infant weight loss by d 3 postpartum. Multidisciplinary studies are needed to standardize the definition of OL and to confirm its validity in different sociocultural contexts.