OBJECTIVE: To assess serial secretory activation biomarker concentrations (sodium [Na], potassium [K], Na: K ratio, protein, lactose, citrate) in mother's own milk (MOM) from pump-dependent mothers of preterm infants to determine associations with coming to volume (CTV), defined as producing at least 500mL/day MOM by day 14 postpartum . STUDY
DESIGN: We collected serial MOM samples and pumped MOM volume data for 14 days postpartum in mothers who delivered at <33 weeks of gestation . Regression models and Mann-Whitney tests were used to evaluate associations .
RESULTS: Of 40 mothers, 39 (mean gestational age 28.8 weeks; 67% overweight/obese; 59% non-white) had paired MOM volume and biomarker data; 33% achieved CTV between days 6-14 postpartum . In univariate models, MOM Na on day 5 and Na: K ratios on days 3 and 5 were associated with CTV . Mothers achieving CTV were more likely to have postpartum Na: K ratios ≤1 on day 3 (75% vs. 25%, P = .06) and ≤0.8 on day 5 (69% vs 10%, p <0.01) compared with mothers not achieving CTV . In a multivariable regression model, day 5 Na: K ratio (1 unit decrease in Na: K, OR 18.7 [95% CI 1.13-311.41], p=0.049) and maternal pre-pregnancy body mass index (BMI) (1 unit increase in BMI, OR 0.88, [95% CI 0.78-0.99], p=0.04) were associated with CTV between days 6-14 .
CONCLUSION: Secretory activation and CTV were compromised in pump dependent mothers with preterm delivery. CTV was predicted by MOM Na and Na: K ratios . These biomarkers hold potential as objective point-of-care measures to detect potentially modifiable lactation problems in a high-risk population.