Nursing care
Why infants of diabetic mothers become hypoglycaemic after birth
Written and reviewed by Dana Whitfield, RN, MSN · 4 min read · Updated October 2026
Short answer
Glucose crosses the placenta but maternal insulin does not, so a fetus exposed to high maternal glucose makes extra insulin of its own. When the cord is cut, the glucose supply stops abruptly but the high insulin output continues for hours or longer. Glucose falls quickly, often in the first hours, which is why early feeding and glucose checks matter.
Start with what crosses the placenta and what does not
Maternal glucose crosses the placenta freely, so when the mother's blood glucose is high, the fetus receives a high glucose load too. Maternal insulin does not cross in the same way. The fetal pancreas responds to the extra glucose by producing more insulin, and over time its insulin-producing cells adapt to that higher workload. The fetus is effectively living in a high-glucose, high-insulin state.
Fetal insulin also acts as a growth signal, which is one reason these babies may be large for gestational age. That size is a visible clue to the hidden problem. However, a baby of normal size can still be exposed to raised maternal glucose, so the maternal history, not birth weight alone, identifies the infant who needs a glucose monitoring plan.
What changes the moment the cord is cut
Clamping the cord ends the continuous glucose infusion from the mother. The baby's pancreas does not switch off its high insulin output at the same moment; it may take hours or even days to adjust. Insulin keeps driving glucose into cells and suppresses the baby's own glucose production, so blood glucose can fall rapidly, often within the first one to two hours.
This is a supply and demand mismatch rather than a disease of the newborn's pancreas. As the insulin response settles and regular feeding establishes, glucose usually stabilises. The nurse's job during the transition is to bridge the gap: provide glucose through early feeding, measure the response, and escalate when feeding is not enough or the baby cannot feed safely.
Recognise expected and concerning findings
Low glucose may produce jitteriness or shakiness, sweating, a fast heart rate, weakness, lethargy, poor feeding or breathing difficulty, and in severe cases seizures. Some infants have low readings without obvious signs, which is why at-risk babies follow scheduled glucose checks rather than waiting for symptoms. A sleepy baby who will not wake to feed deserves a check, not just more time.
A reassuring trend is a baby who feeds early, has readings that rise with feeding, and stays alert and warm. A concerning trend is repeated low readings despite feeding, signs of neurological irritability, or a baby too unwell to feed. Cold stress and respiratory distress increase glucose use, so warmth and breathing assessment belong in the same picture.
Translate the mechanism into nursing care
For an infant of a diabetic mother, start feeding early, ideally within the first hour, support breastfeeding or offer the feed the parents have chosen, and keep the baby warm with skin-to-skin contact. Check glucose at the times set by the unit's newborn protocol and document each value with feeding times. Observational research shows many low readings in these infants are corrected by early feeding.
When glucose remains low despite feeding, or the baby is symptomatic, notify the provider promptly; intravenous dextrose may be needed under the treatment plan. Explain the reasons for heel-stick checks to parents so they understand that the baby is not ill because of something they did. Teach them early feeding cues and to tell the nurse if the baby becomes floppy, jittery or difficult to wake.
Work through a hypothetical exam-style scenario
Picture a hypothetical term newborn of a mother with insulin-treated diabetes. At 45 minutes of age the baby is jittery, and the nurse has not yet fed the baby. The options are to give a bath to stimulate the baby, to wait for the scheduled two-hour glucose check, or to check glucose now and begin feeding. Checking glucose and feeding is the strongest answer.
Bathing risks cold stress, which uses more glucose, and waiting ignores a symptom that may reflect hypoglycaemia. The reasoning tested is that the fetal insulin excess outlasts the cord, so jitteriness in this baby points first to low glucose. If the reading stays low after feeding, or the baby cannot feed, the next step is escalation for further treatment.
Sources and further reading
MSD Manual Professional: Neonatal hypoglycemia. Glucose but not insulin crossing the placenta, persisting fetal insulin after cord clamping, early timing, clinical signs, early feeding and IV dextrose.
PMC: Early feeding and neonatal hypoglycemia in infants of diabetic mothers. Hypoglycaemia often detected in the first hour of life and most episodes corrected by early breast or formula feeding.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our maternity and newborn practice questions are the closest set to what this page covers.
Common questions
Why doesn't maternal insulin protect the baby?
Maternal insulin does not cross the placenta in the way glucose does. The fetus makes its own extra insulin in response to high glucose, and that insulin continues after birth.
When is an infant of a diabetic mother most likely to become hypoglycaemic?
Glucose can fall quickly in the first hours after birth, when the maternal supply has stopped but the baby's insulin output is still high. Unit protocols set the timing of checks.
Does a normal birth weight remove the risk?
No. A large baby is a clue, but an infant of normal size can still have high insulin after exposure to maternal hyperglycaemia, so the maternal history drives monitoring.