It’s a weird experience living in an age where where are obsessed with quantification—we can measure nearly everything in our lives—and then hearing we should just trust our breasts to produce what our babies need. We don’t come with milliliter markers on our breasts, and that can feel hard. It can make us very uncertain about how we’re doing with feeding.

And in some cases, parents are right to be concerned about the baby’s intake.

In the first four months of age, once the milk has ‘come in’ around Day 3-5, you’re looking for the baby to return to birth weight by Day 10-14. Then you’re looking for the breastfed baby to gain 200+ grams per week (30+ grams per day). The weight gain in the first four months is tremendously fast; it has to do with physical development, including the brain’s development. If a baby is consistently not gaining weight at that level, the baby’s physical development, mental development, and stamina for managing feedings can start to be impacted. A baby who’s not taking in enough milk will start drifting down the percentiles on the WHO weight-for-age chart (you can calculate the birth percentile and the current one at infantchart.com). A drop in a few percentiles is not a big deal. A consistent drop in percentiles in the first four months of life is an indication that the baby is not getting enough to eat.

(Is the baby going up the percentiles? That’s okay. There’s no relationship, in the research, between being a chubby breastfed baby and having obesity later in life. There is for formula consumption, but not for breastmilk.)

Your home visit nurse will weigh your baby. If it’s been two weeks since she last visited, and your baby has gained 20 or 80 or 240 grams in fourteen days, instead of the 400+ grams we would expect, that’s an indication that the baby has not taken in enough milk. That inadequate gain can be an issue with the baby’s ability to remove milk from the mother, or the mother’s ability to produce milk, or both, but it is an indication something significant is going on. Sometimes the suggestion from a healthcare provider is to give supplemental milk or formula for a few days to get the weight up; while supplementing can (in some situations) be important, it doesn’t address the underlying issues. Generally speaking, if you stop the supplement, the baby will return to not gaining enough weight. The insufficient weight gain is an indication that the family needs professional support from an IBCLC (International Board Certified Lactation Consultant) to get breastfeeding on track.

Contrary to what you may hear, a baby peeing regularly is not an indication of good milk intake. It’s an indication of some milk intake with good kidney function, so hurray for those healthy kidneys, but it does not indicate a baby is getting enough food.

Occasionally, a well-meaning healthcare provider will tell the parents, “It’s no big deal that the baby’s not gained much weight. It’s wonderful you’re breastfeeding.” I love it when healthcare providers want to encourage families in their breastfeeding journeys. Unfortunately, when a baby is not gaining well, telling parents that the weight gain isn’t important isn’t actually being supportive: if we can catch and deal with these issues in the first few weeks of a baby’s life, we have the best chance of getting the situation turned around without tremendous effort. When a healthcare provider dismisses the baby’s lack of weight gain as a non-concern, it delays the parents seeking the care from an IBCLC that the family needs. Sometimes when that happens, the situation has become complicated and critical by the time a family sees an IBCLC, and it takes several appointments, a good bit of time, and various efforts to turn things around.

Nearly all the moms I see in this situation are worried that the baby is not gaining well because they are positioning or latching the baby incorrectly, and that’s almost never a root cause, so if you’re in this situation, try not to assume you’re doing something basic wrong. (If we can tweak your positioning and latch, great, but it’s very rarely a root cause.) Also, nearly all the moms I see in this situation have had a gut feeling hat something wasn’t going right with feeding. Sometimes these kinds of challenging situations are useful as a way of getting us to learn to listen to our parenting instinct.

In these situations where the baby is not gaining weight well, we start working on what the underlying causes are, and we make sure the baby gets enough to eat to gain weight appropriately so that development stays on track and the baby feels satisfied after meals.