Indicators of Secretory Activation in Mothers of Preterm Very Low Birth Weight Infants

Background Inconsistent information exists regarding indicators of secretory activation in mothers delivering very low birth weight infants. Research aims To compare time to the onset of secretory activation using three separate indicators. A secondary aim examined the association between indicators of secretory activation and milk production. Methods Indicators of secretory activation included maternal perception, volume attainment (production of ≥ 20 mL in two consecutive expression sessions) and biomarkers (sodium and lactose) obtained at volume attainment. Milk production was measured on Days 1–7 and then weekly for 6 weeks. Results In 69 mothers of infants born ≤ 32 weeks’ gestation and < 1500 g, we found no correlation in time to secretory activation between indicators. Earlier volume attainment was associated with increased milk production on Days 1–7, 14, 21, and 28 (all p < .007). Participants who exhibited both normal lactose and sodium levels produced more milk on Days 28 and 42 ( p = .028 and .011), those with only normal lactose levels produced more on Day 42 ( p = .026) and those with only normal sodium levels on Day 28 ( p = .036). Earlier secretory activation by volume attainment was associated with increased expression frequency during Days 2–5 (all p < .014) and participants with normal biomarkers expressed more frequently during Days 2–5 (all p < .020). Conclusion Mothers of very low birth weight infants are at risk for delayed secretory activation, which may decrease their milk production. Frequent expression during the first 5 days postpartum may promote earlier secretory activation. Valid methods of determining secretory activation are necessary to develop interventions promoting earlier secretory activation.

Comparison of Inductively Coupled Plasma Optical Emission Spectrometry with an Ion Selective Electrode to Determine Sodium and Potassium Levels in Human Milk

Sodium (Na), potassium (K), and the ratio Na:K in human milk (HM) may be useful biomarkers to indicate secretory activation or inflammation in the breast. Previously, these elements have been measured in a laboratory setting requiring expensive equipment and relatively large amounts of HM. The aim of this study was to compare measurements of Na and K in HM using inductively coupled plasma optical emission spectrometry (ICP-OES) with small portable ion selective electrode probes for Na and K. Sixty-five lactating women donated 5 mL samples of HM. Samples were analyzed with two ion selective probes (Na and K) and also ICP-OES. The data were analyzed using paired t-test and Bland–Altman plots. Na concentrations were not significantly different when measured with ion selective electrode (6.18 ± 2.47mM; range: 3.59–19.8) and ICP-OES (5.91 ± 3.37 mM; range: 2.59–21.5) (p = 0.20). K concentrations measured using the ion selective electrode (11.7 ± 2.21 mM: range: 7.69–18.1) and ICP-OES (11.1 ± 1.55 mM: range: 7.91–15.2) were significantly different (p = 0.01). However, the mean differences of 0.65 mM would not be clinically relevant when testing at point of care. Compared to ICP-OES, ion selective electrode is sufficiently accurate to detect changes in concentrations of Na and K in HM associated with secretory activation and inflammation in the mammary gland.