Oxytocin, Vasopressin and Prolactin in New Breastfeeding Mothers: Relationship to Clinical Characteristics and Infant Weight Loss.
Elise N Erickson, C Sue Carter, Cathy L Emeis
PMID 31033381WHAT IT FOUND
New mothers whose babies lost less than 5% of birth weight had higher oxytocin and lower vasopressin levels during a feeding.
Higher prolactin was linked to more milk transfer, but oxytocin and vasopressin were not.
Key findings
01Mothers whose infants lost less than 5% of birth weight had significantly higher baseline oxytocin and lower vasopressin than mothers whose infants lost more.
02Prolactin levels were lower in mothers who transferred more than 40 ml of milk, but oxytocin and vasopressin did not correlate with milk transfer volume.
03Women of color had higher prolactin and vasopressin levels than white women, though the authors note this finding is hypothesis-generating due to the small sample size.
STILL TO COME
How it was doneWhat they foundWhat it means for RNs
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What it does not show
Very small sample size (46 enrolled, 35 followed up) and a pilot design with a relaxed significance threshold (p < .10). Participants were healthy, non-obese, English-speaking primiparous women intending to exclusively breastfeed, limiting generalizability. Attrition was high, and 31% of women declined participation, often because they felt overwhelmed, meaning the sample likely represents women coping better with early breastfeeding. Milk transfer was measured at a single time point, which the authors note may not be a sufficient proxy for overall milk production. Self-reported breast fullness is subjective and prone to error.
Declared interests
The authors declared no potential conflicts of interest.
The easy way to misread this
Do not assume that measuring maternal oxytocin or vasopressin can diagnose milk supply issues or that hormone levels cause the weight loss. The study shows an association, not causation, and hormone testing is not a validated clinical tool for lactation assessment.