I had this fabulously scarring episode when I was a very tired resident in which I mentioned during rounds that a patient’s white blood cell count was 13.5 (yes, I still remember that number). My attending stopped me, wrote 13.5 on a piece of paper and threw it into the air. When it landed at my feet, he said “Jenny, what’s that?” I dutifully replied “It’s this child’s white blood cell count.” He then uttered words that have stuck with me forever. “No, it’s a random number flying through the air.”
I told this story first in “Yellow is a Color” and I’m going to continue on theme as we ponder blood sugar (glucose) screening.
First, what’s supposed to happen? What’s normal? Well, a healthy, full- term infant, delivered vaginally, comes out into the world and all sorts of amazing, hardwired things happen. We talked about this is in the “Normal Newborn” so let’s just focus on blood sugar.
In a healthy full term infant, the blood sugar normally drops and then recovers, without intervention, in a couple of hours. The blood sugar recovers through the use pathways that create useable sources of energy, mostly for the brain. In newborns, glucose is not the only source of energy. Glucose and ketone formation (and some other alternate body “fuels”) work together to make sure that the newborn brain does not suffer injury.
This is supposed to happen. This is normal. The baby goes from the placenta-driven world to the real world and has to adapt. The breastfed term newborn has lower blood sugars but higher levels of ketones and other fuels to keep the baby going than formula fed kids. Breastfeed babies are normal. Therefore, this drop in blood sugar that the baby makes up for with ketone bodies is normal.
Since we measure blood glucose and not blood glucose plus ketone- fuel- things- that –make- your brain- happy, we get a number. A number that tells us glucose levels but doesn’t measure alternative sources of energy. A random number flying through the air.
So, let’s say we get a baby who has a measured glucose of 25. Well? Now what?
Does that baby have symptoms? If not, why did we check? Kids without symptoms are doing something right. Why would we “fix” that? That glucose of 25 may mean nothing if the baby makes up for it with creation of alternative fuels, which they do normally, and which we don’t check when we measure “blood sugar.” Kids with no symptoms from their low blood sugar don’t need to be treated. The answer is to do what we should be doing already: skin-to-skin snuggling, feeding within an hour after delivery, and frequent breastfeeding, since breastfeeding is a source of sugar. You can continue to check blood sugars until they are normal, however you define normal and if you checked blood sugars to begin with.
When we treat that symptom-less blood sugar with something other than breastmilk, the production of alternative fuels gets messed up. Low blood sugar drove those pathways to create alternative fuel production. When we give formula or glucose water we don’t need other ways of finding sugar- it’s right there and those other newborn pathways may be delayed in working. We messed with physiology. That wasn’t nice because now, without those helping pathways, the kids may need continued supplements.
A baby with a low blood sugar and symptoms, well, that’s a problem. Symptomatic blood sugar can show up as irritability, seizures, lethargy, turning blue, coma, not being able to maintain your temperature, irregular breathing, among other evil things. Now look at that list and see if we want to chalk any or one of those symptoms up to just a low blood sugar. That baby could be sick. Really sick. Like "take them to the ICU sick."
What’s up with that baby that they didn’t compensate for their low glucose with those ketone bodies? What went wrong? Maybe the baby is a premie and can’t create ketone bodies or alternative body fuel. Maybe the baby is simply cold and should be snuggling on mom’s chest. Or maybe that baby has overwhelming infection, congenital heart disease, lung disease, liver disease or is otherwise really sick. Kids with low blood sugar and symptoms can have awful neurological problems. Why though? Because of the blood sugar itself or because of the underlying reason the baby couldn’t make up for that normal drop in blood sugar?
SO…
Low blood sugar with no symptoms. Not an issue.
Breastmilk meets the nutritional requirements of healthy, term infants and those same healthy term exclusively breastfed infants do not develop symptomatic low blood sugar because they are not eating. Healthy term infants do not need to have their blood sugar screened.
Low blood sugar with symptoms: Big problem.
These children have some reason they can’t make up for low blood sugar with other fuels. They may be, among other things, premature, small for gestational age, an infant of a diabetic mother (especially if the diabetes was poorly controlled), be sick, or be withdrawing from a substance mom was taking. Those kids should be screened. Because then, the number means something.
Jenny Thomas, MD, IBCLC, FAAP, FABM