The 'Magic Number' and Long-Term Milk Production (Part 1)

In my last blog post, I told a military mother who had returned to work at six weeks postpartum that she was making as much milk as her thriving baby would ever need.  To meet her breastfeeding goal of one year, I told her, “all she had to do was maintain her milk production.”  But maintaining milk production is not always easy for employed mothers, especially when they don’t know the basic dynamics affecting how much milk they make.  I shared some of these dynamics with this mother, and my explanation set her mind at ease.

Breast storage capacity.  This is the amount of milk in a woman’s breasts when they are at their fullest each day and this amount can vary greatly among mothers.  Breast storage capacity affects how many times every 24 hours a woman’s breasts need to be drained well of milk—either by breastfeeding or expression—to maintain her milk production.  When her breasts become full, this sends her body the signal to make milk slower.  In other words, “drained breasts make milk faster” and “full breasts make milk slower.”  The amount of milk needed to slow milk production will be much greater in a woman with a large breast storage capacity, so she can remove her milk fewer times a day without her milk production decreasing

The “magic number.”  This refers to the number of times each day a mother’s breasts need to be well drained of milk to keep her milk production stable.  Due to differences in breast storage capacity, some mothers’ “magic number” may be as few as 4-5 or as many as 9-10.  But when a mother’s total number of breast drainings (breastfeedings plus milk expressions) dips below her “magic number,” her milk production slows.

Daily totals.  Many of the employed breastfeeding mothers I help by phone are diligent about maintaining their number of milk expressions at work, but often, as the months pass, they breastfeed less and less at home.  With this change in routine, they may drop below their “magic number,” which causes a dip in milk production. 

Recently, as I asked one employed mother with decreasing milk production about her daily routine, she told me that her baby was sleeping in a swing all night.  She discovered that in the swing he did not wake at night to feed, so she was sleeping on the couch in her living room next to the swing and waking every hour to check on him.  I told her that eliminating those nighttime breastfeedings was the likely cause of her decreased milk production and I asked if she thought returning to breastfeeding at night might mean more sleep for her as well as more milk for her baby.

More breastfeeding when together means less expressed milk needed.  The amount of milk per day babies need between 1 and 6 months stays remarkably stable, on average between 25 and 35 oz. (750-1050 mL) per day.  By thinking of the 24-hour-day as a whole, it becomes obvious that the more times each day the baby breastfeeds directly, the less expressed milk will be needed while mother and baby are apart.  But many mothers don’t realize that dropping breastfeedings at home and encouraging baby to sleep more at night adds to the amount of expressed milk their baby needs during the day.  Understanding these basic dynamics can go a long way in helping mothers meet their long-term breastfeeding goals.