Low Blood Sugar in Babies Born a Little Early: Does It Affect How They Develop?

What a 2026 New York study of 128 toddlers tells families about newborn blood sugar checks

A 2026 study from four hospitals in New York followed 128 children who were born a few weeks early, at 35 or 36 weeks of pregnancy, to see whether low blood sugar in their first day of life affected how they were developing at around 18 to 24 months. Babies whose blood sugar had dipped low, and who had been checked and treated by the hospital team, were doing about as well as babies whose blood sugar had stayed normal. The result is encouraging for families, although the researchers say longer follow-up is still needed [1].

Why newborn blood sugar gets so much attention

Sugar, or glucose, is the main fuel for a baby's brain. Before birth, a baby receives a steady supply through the placenta. After the cord is cut, the baby has to switch to getting fuel from feeds and from its own body's stores, and that takes some adjustment. Babies born a few weeks early, called late preterm babies, can find the switch harder, because their bodies are less mature and they may be sleepy and slow to feed. As a result, low blood sugar is one of the most common issues in the first hours of life, and nurseries routinely check the blood sugar of babies who are at higher risk.

Doctors check because they worry about the brain. If blood sugar stays very low for too long, the brain can be harmed. But no one knows exactly how low is too low, or for how long. This is why the checking and treating of newborn blood sugar is such an important topic for families and doctors alike.

How doctors decided what counts as "low"

In 2011, the American Academy of Pediatrics, a large organization of children's doctors, gave guidance on when to treat. In the first four hours of life, a blood sugar below 40 mg/dL (a standard unit for blood sugar) counts as low and calls for action. Between four and 24 hours, below 45 mg/dL does [2]. Another group, the Pediatric Endocrine Society, which focuses on hormone problems that can cause persistent low sugar, suggested higher targets for babies whose low sugar does not go away. The New York study describes these as more than 50 to 60 mg/dL [3][1]. These numbers were agreed by experts as safe, practical lines to draw. They were not based on proof that a particular number leads to a particular problem.

Over the years, researchers have tried to find out whether low blood sugar in a baby really leads to problems later. A long-running study in New Zealand followed babies who were at risk of low blood sugar. A doctor who wrote about it in 2026 explained that these children seemed to be developing normally at 2 years of age, but at 4.5 years some had trouble with executive function, which means skills such as planning, remembering instructions and controlling impulses [4][5][6]. Other studies looked at how children did at school and on thinking tests when they were older [7][8][9], including children who had taken part in a trial of a sugar gel rubbed inside the baby's cheek to prevent low blood sugar, called the hPOD trial [10]. The same commentary says that in one earlier group about half of the children had thinking difficulties at ages 9 to 10 [4].

Because of these findings, many families and doctors have worried that a low reading in the first day might cast a shadow years later. At the same time, a trial in the Netherlands tested whether treating a little later might be safe. Healthy newborns with moderately low sugar and no symptoms were treated either at 47 mg/dL, the traditional line, or at a lower line of 36 mg/dL. The lower line turned out to be just as good for the children's movement and development at 18 months [11]. A recent review asks, in its title, whether we can find a safe glucose threshold at all [12]. Doctors still did not have clear answers about late preterm babies cared for in an ordinary nursery by following the American Academy of Pediatrics guidance.

What the New York researchers did

The researchers worked in four hospitals: Jack D. Weiler Hospital, Wakefield Hospital and Jacobi Medical Center in the Bronx, and White Plains Hospital in Westchester County. From August 2021 to July 2024, they enrolled babies who were born at 35 or 36 weeks, weighed at least 2,000 grams (about 4 pounds 6 ounces) and stayed in the regular newborn nursery [1]. Babies were left out of the study if they had serious birth defects, a severe lack of oxygen at birth, or illnesses that needed intensive care, or if their families could not be reached or did not speak English, because the test used at the follow-up visit was not available in other languages.

In the first 24 hours the nursery checked each baby's blood sugar with a small finger- or heel-prick test and followed the American Academy of Pediatrics rules. Babies whose sugar went low were helped with extra feeds, with a gel that is rubbed into the cheek, or with sugar given through a drip if needed. When the children were about 22 months old, on average, a trained examiner used a well-known developmental test, called the Bayley test, to look at thinking, language, movement, social and emotional skills and everyday adaptive skills. In all, 128 children completed the test: 81 had had low blood sugar and 47 had not [1].

What the researchers found

The scores of the two groups were almost the same. For example, the average thinking score was 93.9 for children who had had low blood sugar and 94.0 for children who had not. Language scores averaged 83.6 and 84.9, and movement scores 96.2 and 94.3 [1]. Looking at how many children had scores low enough to suggest a delay (below 70), the shares were also similar. Among those who had had low blood sugar, 6.2% had a low thinking score, compared with 6.4% of those who had not.

The researchers also looked at the babies whose sugar had dropped the furthest, below 36 mg/dL, and at those who had three or more low readings. In general, their results were similar too. One exception is that among babies with very low sugar, a larger share had language scores in the "borderline" range, which is a little below average but not a delay (43.2% versus 20.9%). Because few babies were in this group, the researchers treat that as something to check in future studies rather than a firm conclusion [1]. Another piece of reassurance comes from a separate, larger study of children followed to age 6 or older after their mothers received steroid injections before late preterm birth. According to a news summary of it, children who had low blood sugar as newborns were no more likely to have thinking scores below the average range than those who did not (about 16% compared with 18%) [13].

What this means for your baby and your family

If your late preterm baby has a low blood sugar reading in the first day and the team feeds, treats and rechecks it, this study suggests that it is unlikely to hold back your child's development in the first two years. The researchers conclude that quickly spotting and treating brief dips in blood sugar, along with early feeding and sugar gel, can help limit the risk of harm [1]. That does not mean that blood sugar does not matter. The babies in this study were checked and treated, which is exactly what the nursery team is trying to do for yours.

It also does not mean that a normal result at 2 years is the last word. The Bayley test gives a good overall picture of a toddler, but it is less able to pick up planning and concentration difficulties, which usually become clear at school age [1]. The doctor who commented on the study makes the same point and says that early normal development does not rule out later problems [4]. If your baby had very low or repeated low readings, ask your pediatrician about keeping an eye on development through the preschool years. You can encourage your child's learning and language in everyday ways: reading, talking and playing together.

There are also reasons to treat the study with care. Only 128 children were tested out of many more who were eligible, and the researchers did not have information about each family's income, which can also affect child development [1]. The study did not include babies born before 35 weeks, babies who needed intensive care for breathing problems or infection, or families who did not speak English. So the results may not apply to every baby.

What researchers are working on next

The researchers say that larger studies that follow children to school age are needed, with tests designed to measure planning, attention and coordination [1]. Open questions include whether continuous glucose sensors, which measure blood sugar around the clock instead of with occasional finger or heel pricks, could show which babies really are at risk, and whether the sugar gel changes development in later childhood. For now, nurseries will carry on checking at-risk babies, and families can feel reassured, though not complacent.

Key points for families

Low blood sugar is common in babies born a few weeks early, and checking and treating it is a normal, safe part of nursery care. In this New York study, children who had had low blood sugar and had been treated were developing similarly to children who had not at about 18 to 24 months [1]. Longer follow-up is still needed, so keep going to your child's check-ups and speak up about any concerns.

References

  1. Balasundaram P, Gorti N, Latuga M, et al. Neonatal hypoglycemia and neurodevelopment outcomes among late preterm infants: a prospective cohort study. Pediatr Res. 2026 (published online 30 May 2026). doi:10.1038/s41390-026-05101-5 ↩
  2. Adamkin DH; Committee on Fetus and Newborn. Postnatal glucose homeostasis in late-preterm and term infants. Pediatrics. 2011;127(3):e20103851. doi:10.1542/peds.2010-3851 ↩
  3. Thornton PS, Stanley CA, De Leon DD, et al. Recommendations from the Pediatric Endocrine Society for evaluation and management of persistent hypoglycemia in neonates, infants, and children. J Pediatr. 2015;167(2):238-245. doi:10.1016/j.jpeds.2015.03.057 ↩
  4. Felderhoff-Müser U. Late preterm hypoglycemia through the lens of long-term evidence. Pediatr Res. 2026 (published online 2 August 2026). doi:10.1038/s41390-026-05316-6 ↩
  5. McKinlay CJD, Alsweiler JM, Ansell JM, et al. Neonatal glycemia and neurodevelopmental outcomes at 2 years. N Engl J Med. 2015;373(16):1507-1518. doi:10.1056/NEJMoa1504909 ↩
  6. McKinlay CJD, Alsweiler JM, Anstice NS, et al. Association of neonatal glycemia with neurodevelopmental outcomes at 4.5 years. JAMA Pediatr. 2017;171(10):972-983. doi:10.1001/jamapediatrics.2017.1579 ↩
  7. Shah R, Dai DWT, Alsweiler JM, et al. Association of neonatal hypoglycemia with academic performance in mid-childhood. JAMA. 2022;327(12):1158-1170. doi:10.1001/jama.2022.0992 ↩
  8. Rozance PJ. Hypoglycemia in the newborn and neurodevelopmental outcomes in childhood. JAMA. 2022;327(12):1135. doi:10.1001/jama.2022.2456 ↩
  9. Roeper M, Hoermann H, Körner LM, et al. Transitional neonatal hypoglycemia and adverse neurodevelopment in midchildhood. JAMA Netw Open. 2024;7(3):e243683. doi:10.1001/jamanetworkopen.2024.3683 ↩
  10. Edwards T, Alsweiler JM, Gamble GD, et al. Neurocognitive outcomes at age 2 years after neonatal hypoglycemia in a cohort of participants from the hPOD randomized trial. JAMA Netw Open. 2022;5(10):e2235989. doi:10.1001/jamanetworkopen.2022.35989 ↩
  11. van Kempen AAMW, Eskes PF, Nuytemans DHGM, et al. Lower versus traditional treatment threshold for neonatal hypoglycemia. N Engl J Med. 2020;382(6):534-544. doi:10.1056/NEJMoa1905593 ↩
  12. Garg M, Devaskar SU. Exploring the long-term impacts of neonatal hypoglycemia to determine a safe threshold for glucose concentrations. Eur J Pediatr. 2025;184(4):263. doi:10.1007/s00431-025-06082-z ↩
  13. Gyamfi-Bannerman C, de Voest JA, Tita ATN, et al. Child neurodevelopmental outcomes after late preterm hypoglycemia. Obstet Gynecol. 2026 (published online 16 July 2026). doi:10.1097/AOG.0000000000006366 ↩