Newborn low blood sugar and brain injury

How does this happen?

Before birth, a baby gets a constant supply of glucose across the placenta. At delivery that supply stops instantly. The baby then has to switch to using their own stores and making their own glucose.

Almost every newborn's blood sugar dips in the first one to two hours while that switch happens, and then recovers. That dip is normal. ²

Some babies cannot make the switch.

• A baby whose mother had diabetes has been producing extra insulin to handle the extra sugar crossing the placenta. After birth the sugar supply stops and the insulin does not, so the level crashes. ⁴
• A baby who is small or growth restricted has few stores to draw on. ²
• A baby born late preterm has an immature system for making glucose.
• A baby who is cold, infected, or stressed burns through what they have faster.

If the level stays low, the brain runs out of fuel. The occipital lobes at the back of the brain, which process vision, are characteristically affected, which is why cortical visual impairment is a common consequence. ³

What causes it?

Two different questions get mixed together here. The first is what leads to this injury in the body. The second is whether anyone could have prevented it. They are not the same question, and the answer to the first does not settle the second.

Happens even with perfect care

• Maternal diabetes, including well-controlled gestational diabetes. ⁴
• Being small for gestational age or growth restricted.
• Being large for gestational age. ⁵
• Late preterm birth, between 34 and 36 weeks.
• Infection or a difficult transition at birth.
• Congenital hyperinsulinism and other rare conditions where the body makes too much insulin regardless of care. ¹
• A slow start to feeding, which happens in many families and is not a failing.

Associated with gaps in care

These are situations where published standards say what the care team should watch for and do. A gap here does not prove anyone caused your child's injury. It points to where the medical records will have an answer.

• A baby with a named risk factor not screened, or not screened on the recommended schedule. Guidance sets out who and when. ² See missed hypoglycemia.
• A low reading not rechecked, or not confirmed on a laboratory sample when the bedside meter reads low. Bedside meters are less accurate at low levels, which is why confirmation matters. ²
• A low level treated once and not followed up, with no recheck to confirm the level came up and stayed up.
• Intravenous glucose not started when feeding alone was not working.
• Persistent low glucose not investigated for an underlying cause such as hyperinsulinism. ¹
• Symptoms attributed to something else, such as jitteriness, sleepiness or poor feeding put down to normal newborn behavior.
• Maternal diabetes not identified in pregnancy, where screening guidance exists. ⁴

Whether any of this amounts to a departure from the standard of care takes a physician expert reading the whole record. The records here are unusually specific: every glucose value has a time attached.

What are the signs, by age?

Signs change as a child grows. A newborn cannot show you a walking problem. Some children look fine at first and show differences months later.

At birth and the first hours

Often nothing at all. Many babies with low blood sugar have no symptoms, which is the whole reason risk-based screening exists. ²

When there are signs they can include jitteriness, a weak or high-pitched cry, floppiness, poor feeding, sweating, a bluish color, low temperature, apnea, or seizures.

The first week

• Seizures, which can be the first obvious sign of significant low blood sugar. ⁶
• Poor feeding and sleepiness.
• Repeated low readings despite feeding.

Around 3 months

• Poor visual attention: not fixing on a face, not following an object. This can be the first sign of cortical visual impairment. ⁷
• Differences in tone.
• Feeding difficulty.

Around 6 months

• Delay in rolling. ⁸
• Difficulty finding objects visually, particularly in a busy background.
• Seizures.

Around 12 months

• Not sitting independently. ⁸
• Visual difficulties that a standard eye test does not explain, because the eye is normal and the brain is not. ⁷

Toddler years

• Motor delay or cerebral palsy.
• Vision that varies with fatigue and clutter.
• Speech and learning delay.
• Epilepsy in some children. ⁹

School age

• Learning differences, particularly visual and spatial.
• Ongoing epilepsy in a minority.
• Visual difficulties that need environmental adjustments rather than glasses.

How is it diagnosed?

Finding low blood sugar

A bedside glucose meter is used for screening. A low reading is confirmed on a laboratory sample, because bedside meters lose accuracy at exactly the low end where the decision matters. ²

Screening is done at set times: before feeds and at defined intervals in the first hours and days, with the schedule set by the risk factor. ²

There is genuine professional disagreement about the exact number that should trigger treatment, and the AAP and Pediatric Endocrine Society approaches differ. ^{2 1} What both agree on is that a persistently low level needs treatment and that a level that will not come up needs investigation.

Investigating persistent low sugar

If glucose stays low beyond the first days, the workup looks for a cause: insulin, cortisol, growth hormone and metabolic testing drawn at the moment the sugar is low, which is called a critical sample. Drawing it at the right moment matters, because the results are only interpretable when the glucose is actually low. ¹

Finding brain injury

MRI shows a characteristic pattern of injury at the back of the brain in the occipital lobes. ³

EEG if there were seizures. ⁶

Vision assessment, asking specifically about cortical visual impairment, because a standard eye exam will be normal. ⁷

What is the treatment?

Treatment escalates by level and by whether the baby has symptoms.

• Feeding, either breast or formula, for mild low readings in a well baby, with a recheck afterward. ²
• Oral dextrose gel rubbed inside the cheek, which is now widely used and reduces the need for intravenous treatment and admission.
• Intravenous glucose when the level is very low, when there are symptoms, or when feeding has not worked. This means admission to a special care or intensive care unit.
• Rechecking after every intervention. A single normal recheck is not the end of it in a baby with ongoing risk. ²
• Treating the underlying cause if glucose remains low, which may include medicines for hyperinsulinism. ¹

After brain injury, care follows the pattern of injury: early intervention therapy, vision support, and seizure treatment where needed. ¹⁰

What is the long-term outlook?

Most babies with a brief low reading that is treated promptly have no lasting effects at all. This is the great majority. ²

Where the level was very low, lasted a long time, or caused seizures, the risk of lasting injury rises. The characteristic pattern involves vision, and cortical visual impairment is the most common consequence, sometimes with learning differences, motor difficulty or epilepsy. ³

The MRI is the most useful guide to what to expect. Ask what it showed and whether the occipital regions are involved.

What does daily life look like?

Where there was no injury, none of this applies and the episode becomes a line in the medical history.

Where cortical visual impairment is present, daily life changes in ways that are easy to misread. A child may see one toy on a plain floor and not find the same toy in a cluttered box. That is not inattention or defiance. The adjustments are environmental: reduce clutter, use high contrast, present one thing at a time, allow extra time for looking, and expect vision to be worse when the child is tired.

At school, visual load is the thing to write into the IEP: plain worksheets, uncluttered displays, and time to look before being asked to respond.

What does care cost over a lifetime?

No agency publishes a lifetime cost specific to hypoglycemic brain injury.

Where it leads to cerebral palsy, the published anchor is CDC's estimate of about $921,000 in 2003 dollars. Where it causes vision impairment, CDC estimated about $566,000 in 2003 dollars for vision impairment. ¹¹ These are separate population estimates that overlap, and they cannot be added together for one child.

See the cost of care estimator.

What can you do this week?

1. Request every glucose value with the time it was taken. This is the core record.
2. Ask which risk factors your baby had and what screening schedule that put them on.
3. Ask whether any low bedside reading was confirmed on a laboratory sample.
4. Ask what was done after each low reading, and what the recheck showed.
5. Ask for a vision assessment and use the words "cortical visual impairment."
6. Ask whether an MRI was done and whether the occipital lobes are affected.
7. Refer to early intervention.

What should you ask each specialist?

Take these with you. Write the answers down in the moment, because you will not remember them later.

For the neonatologist

• What were all the glucose values and their times?
• What risk factors did my baby have, and what screening schedule did that require?
• Were low bedside readings confirmed in the laboratory?
• How long was the glucose low before it came up and stayed up?
• Was a critical sample drawn while the sugar was low?

For the neurologist

• What did the MRI show, particularly at the back of the brain?
• Were there seizures on EEG?
• What should we watch for over the next year?

For the ophthalmologist or vision specialist

• Is this cortical visual impairment rather than an eye problem?
• What should we change at home so my child can see more easily?
• Who assesses functional vision, as opposed to eye health?

You can also build a printable list with the question generator.