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Objective: An efficient method for measuring maternal milk production is needed. Our objectives were to: (1) validate a milk production rate (MPR) protocol in exclusively breastfeeding mothers; (2) determine MPR change following 48 hours of increased breast emptying; (3) assess agreement between MPR and infant test-weighing; and (4) characterize MPR in early postpartum exclusively breastfeeding mothers. Materials and Methods: N = 23 mothers emptied both breasts hourly over 3 hours (h0, h1, h2, and h3). We estimated steady-state MPR as mean (h2 and h3). Subset A mothers (n = 5) also completed MPR measurements after 48 hours of increased breast emptying. Subset B mothers (n = 16) also test-weighed for 48 hours. We used paired t-test to examine within-participant change in hourly milk yield and MPR; and we used Bland-Altman analysis to compare 24-hour milk production (g/24 hours) measured using test-weight versus MPR. Results are reported as mean ± standard deviation or (±95% limits of agreement). Results: Mothers were 54 ± 14 days postpartum. Paired difference in h3–h2 hourly milk yield was not significantly different (p > 0.05, 3 ± 10 g/hour). In Subset A (n = 5), MPR declined from 50 ± 13 to 43 ± 16 g/hour (p = 0.003) following 48 hours of increased breast emptying. In Study B (n = 16), mean infant test-weighed intake (TW) was 717 ± 119 g/24 hours, and mean MPR was 1,085 ± 300 g/24 hours. Mean difference (MPR-test-weigh) and mean ratio (MPR/test-weigh) significantly increased as MPR increased (p 20 g/24 hours, n = 12), mean MPR = 48 ± 12 g/hour (range, 35–78 g/hour). Conclusion: MPR is a valid measure of current maternal milk production capacity, but is not accurate for evaluating infant intake in exclusively breastfeeding dyads.

OBJECTIVES: Measuring maternal milk production is cumbersome. Our objectives were to: 1) confirm that milk production rate reaches steady state at hour 2 of hourly breast emptying; and 2) compare agreement in milk production when measured using the well-established test-weighing method versus the more efficient hourly breast emptying method (Lai, et al., Breastfeeding Medicine, 2010). METHODS: Eligible mothers were 4–10 weeks postpartum and exclusively breastfeeding their healthy, singleton, term infants. A subset of mothers test-weighed (TW) their infant (± 2 g) before and after breastfeeding for 48h. Within 1 week of TW, mothers had a morning visit at the research clinic for hourly breast expression measurements. Mothers emptied both breasts at baseline (h0), and 1, 2, and 3 hours after baseline (h1, h2, h3) using a hospital-grade pump. We recorded hourly milk output ± 1 g and adjusted production rate (g/h) to exact interval (minutes from end of previous to end of current expression). We used paired t-test to compare g/h at h3 versus h0, h1, and h2. We estimated mother's steady-state milk production rate (MPR, g/h) as mean (h2, h3). We used the Bland-Altman method for determining the 95% limits of agreement in measuring milk production (g/24h) using TW versus MPRx24. RESULTS: 23 mothers (65% primiparous) were 54 ± 14 days postpartum. Milk output was 185 ± 55 g at h0 and 60 ± 26, 47 ± 13, 44 ± 13 g/h at h1, h2, and h3, respectively. Mean paired difference (vs. h3) was significant at h0 and h1 (P 0.05, h3 - h2 = 3 ± 10 g/h). In the subset with TW data (n = 16), mean TW milk output was 717 ± 119 g/24h, and mean MPRx24 was 1085 ± 300 g/24h. Mean difference, MPRx24 - TW [± 95% limits of agreement], was 368 [± 468] g/24h; and mean ratio, MPRx24/TW, was 1.5 [± 0.4]. Both difference and ratio significantly increased as MPR increased (P