WWYD - 5 wks from 1st b-day and pump on the outs

willisbf

Just discovered that my breast pump is dieing. I've got some breast milk frozen, so I have some I can send to school with LO. I'll continue to bf at home. How/when would you start the transition to cow's milk? I know 12 months is "the" time....would you start mixing a little into the thawed frozen milk a little early?