Feasibility and Acceptability of Metformin to Augment Low Milk Supply: A Pilot Randomized Controlled Trial.

This was a pilot with only 15 randomized participants (10 metformin, 5 placebo), and the trial did not reach its planned sample size of 30, so it cannot establish whether metformin improves milk supply. The main objectives were feasibility, acceptability, tolerance, safety, and measurement success, not a definitive test of efficacy; the milk-output comparison was preliminary. Milk output did not differ significantly between groups (p=.28), and the overall mean change was -9 mL/24 hr, so the pilot did not show a clear increase in supply. Eligibility criteria for insulin resistance and liver or kidney function were expanded during recruitment, which changes who was studied and limits generalizability. Insulin resistance was defined by broad clinical signs rather than a definitive diagnostic test, so unknown non-metabolic causes of low milk supply could have affected results. Enrollment occurred later than intended, with median enrollment 3 weeks after the ideal 1 to 2 weeks postpartum, and some eligible mothers declined because they did not want medication while breastfeeding or were discouraged by very low baseline output. The 24-hour test-weigh method was burdensome in mothers who were breastfeeding, pumping, and giving supplemental feeds, which may affect feasibility and acceptability. The significance threshold was p<.10 for this pilot, and some analyses were post hoc, so trends should not be treated as confirmatory.

The authors declared no potential conflicts of interest. The supplied text does not report a funding source. The study drug was Glucophage XR (Bristol Myers Squibb), and placebo was supplied by PCCA.

Do not conclude that metformin increases milk supply. The pilot randomized 15 mothers, its primary objectives were feasibility and acceptability, and maximum milk output did not significantly improve versus placebo (p=.28).