Table 1:

Measures of Lactation Outcomes

Measures	Method	Strengths	Limitations
Milk Volume	Maternal self-report	Easy to learn Requires only a journal or diary	High risk for error Requires maternal compliance Recall bias
	Weighing vials of expressed milk	Likely most accurate technique Requires an accurate and precise scale Can be used to validate maternal report of volume and pumping frequency Potential to blind individuals weighing milk	Training required for accuracy Time consuming Relies on mothers bringing all vials of expressed milk to the NICU
	Visualizing milk vial graduations	Easy to learn Requires no equipment	Relies on nurse documentation or maternal report Relies on precision of volume graduations on vials Potential high error rate
	Test-weighing	Validated method to measure milk volume during breastfeeding	Time consuming Requires a precise infant scale Training required
Lactation Duration	Infant consumption at discharge	Easily collected from medical records	Does not include post-discharge data Infants may be receiving MOM when mothers are no longer lactating Varies depending on length of hospital stay Excludes other health relevant time-points during hospitalization as well as dose of MOM received
	Infant consumption at different time-points during hospitalization	Data easily collected from medical records Considers timing of consumption	Infants may receive MOM when mothers are no longer lactating
Onset of Secretory Activation	Production of ≥20mL of milk in two consecutive expression sessions	Easy to measure	May reflect a mother’s ability to effectively remove milk from her breasts Relies on accurate measurement of milk volume
	Maternal report of sudden breast fullness	Validated in mothers of term infants No equipment or training required	Unknown validity in mothers of preterm infants Mothers should be questioned daily to reduce recall bias
	Biomarkers contained in MOM	Validated in mothers of term Infants Likely most accurate indicator Reflects changes at the physiological level	Validity not established for mothers of preterm infants Cut-off levels not established for mothers of preterm infants

Note. NICU = neonatal intensive care unit; MOM = Mother’s own milk