A Common Diabetes Pill May Help Protect Premature Babies From Low Blood Sugar

What a new randomized study of metformin and steroid injections means for families facing an early birth

When a baby is likely to be born early, mothers are usually given a steroid injection called betamethasone that greatly improves the baby's chances by helping the lungs mature. That injection has one well-known side effect: it briefly raises the mother's blood sugar, which can make the baby's blood sugar drop too low in the first hours after birth. A new randomized study of 169 women found that adding metformin — an inexpensive, widely used diabetes tablet — during the two days after the steroid roughly halved how often premature babies developed low blood sugar, from 40% down to 21%, with only mild and mostly stomach-related side effects for the mothers. It is the first strong evidence that treating the mother can prevent this particular newborn problem before it starts.

Why This Matters, and How Families Faced It Before

To understand the finding, it helps to know why the steroid is given at all. For decades, doctors have known that a course of betamethasone before an early birth is one of the most protective things they can do: it lowers the risk of serious breathing trouble, bleeding in the brain, and death in premature babies, a benefit confirmed across many trials [1] and recommended by obstetric guidelines worldwide [2]. The trade-off became especially visible when a large trial called ALPS extended the steroid to babies born just a few weeks early. It confirmed the breathing benefit but also showed that more of the steroid-exposed babies had low blood sugar after birth — about 24%, compared with 15% of those not exposed [3].

The reason is a chain reaction. The steroid raises the mother's blood sugar for roughly two days. Extra sugar crosses to the baby before birth, and the baby's body ramps up insulin, the hormone that lowers blood sugar. After birth, when the mother's sugar supply is suddenly cut off, the baby is briefly left with too much insulin and not enough sugar. Premature babies are hit hardest because they have very small reserves of stored energy to fall back on [4]. Low blood sugar in a newborn matters: it can cause jitteriness, poor feeding, and in more serious cases affect the developing brain, so nurseries take it seriously [5][6].

For years, the only way families and clinicians dealt with this was to wait and watch. Babies at risk would have their blood sugar checked repeatedly with heel-prick tests after birth, and if it dropped, the team would respond — with early feeding, a sugar gel rubbed inside the cheek, or a sugar drip into a vein [7]. These steps work well, but they all happen after the low sugar has already occurred, often meaning extra tests, a stay in the neonatal intensive care unit (NICU), and sometimes separation of mother and baby at a stressful time. No one had tested whether treating the mother during the steroid window could stop the problem before it began [8].

What the Researchers Did

Researchers at three university hospitals in Israel enrolled 169 pregnant women who were getting betamethasone because they were at risk of delivering early, between 24 and about 36 weeks of pregnancy [8]. Women who already had diabetes were not included, because they receive blood-sugar treatment anyway. By the flip of a computerized coin, half the women were given metformin tablets for up to two days after the steroid, and half were given no blood-sugar medication. Everything else — the steroid dose and the blood-sugar checks — was the same for both groups. Metformin is not a new or experimental drug here: it is the same tablet doctors routinely use for diabetes in pregnancy, so its general safety in pregnancy is already well studied [9]. The doctors caring for the newborns did not know which mothers had received metformin, which helps keep the results fair and unbiased [8].

What They Found

The mothers who took metformin had lower average blood sugar than those who did not — a real but modest difference [8]. The result that matters most to families was in the babies. Among the premature infants, low blood sugar occurred in about 21% of those whose mothers took metformin, compared with 40% of those in the comparison group — close to half as often [8]. That benefit appeared even though, by chance, the metformin group started with some features that usually make low blood sugar more likely, which makes the result more convincing rather than less. Other aspects of the babies' health — their birth weight, time in the NICU, breathing problems, and jaundice — were similar in both groups, suggesting the drug specifically helped with blood sugar rather than changing everything else [8]. For the mothers, the main downside was tolerability: about one in seven had mild side effects, usually an upset stomach, and some chose to stop the tablets. No mother's blood sugar dropped too low [8].

What This Means for Your Family

If you are facing a possible early birth, the most important takeaway is reassuring: the steroid injection remains strongly worth having, because its benefits for the baby's lungs and survival are large and well established [1]. This study does not change that. What it adds is an encouraging possibility — that a familiar, low-cost tablet taken for just a couple of days might reduce the chance of one of the steroid's side effects in the baby. It is important to be clear about what the study does and does not yet show. It was a single, relatively small trial in one country, it involved mothers who did not have diabetes, and the best dose of metformin is still being worked out. For those reasons, metformin is not yet a routine part of care everywhere, and whether it is right in any particular pregnancy is a decision for your own medical team. If your baby is born early, you can still expect the nursery to check blood sugar carefully and to treat it quickly if needed — that safety net stays firmly in place [7]. The value of this research is that it points, for the first time, toward preventing the problem rather than only reacting to it.

It can also help to understand why this approach is appealing to doctors beyond the results themselves. Metformin is a very old, very familiar medicine. It is taken by mouth rather than by injection, it is inexpensive, and it does not need refrigeration or special equipment to use. That combination means that, if larger studies confirm the benefit, it could be a practical option in many kinds of hospitals — not only large, well-resourced centers. At the same time, the honest picture includes the downsides the study found: the tablets can upset the stomach, and a number of women in the study chose to stop them. Any decision about using metformin this way is something to weigh together with your care team, taking into account your own situation and preferences. The point of sharing this research is not to suggest that families should ask for a specific medication, but to show the direction that newborn care is moving — toward gently heading off problems in advance rather than only treating them once they appear.

What Researchers Are Working On Next

Scientists now want to confirm this result in larger studies across different countries and hospitals, to pin down the best dose, and to compare metformin with other options such as insulin [8][9]. They also plan to follow the children as they grow to make sure the approach is safe in the long run — an area where metformin already has reassuring track record from its long use in diabetes during pregnancy [10]. For families, the encouraging bottom line is that a decades-old, unavoidable-seeming side effect of a life-saving treatment may turn out to be something doctors can gently prevent.

References

  1. McGoldrick E, Stewart F, Parker R, Dalziel SR. Antenatal corticosteroids for accelerating fetal lung maturation for women at risk of preterm birth. Cochrane Database Syst Rev. 2020;12(12):CD004454. doi:10.1002/14651858.CD004454.pub4 ↩
  2. Committee on Obstetric Practice. Committee Opinion No. 713: Antenatal Corticosteroid Therapy for Fetal Maturation. Obstet Gynecol. 2017;130(2):e102-e109. doi:10.1097/AOG.0000000000002237 ↩
  3. Gyamfi-Bannerman C, Thom EA, Blackwell SC, et al. Antenatal Betamethasone for Women at Risk for Late Preterm Delivery. N Engl J Med. 2016;374(14):1311-1320. doi:10.1056/NEJMoa1516783 ↩
  4. Stanley CA, Rozance PJ, Thornton PS, et al. Re-evaluating "transitional neonatal hypoglycemia": mechanism and implications for management. J Pediatr. 2015;166(6):1520-1525.e1. doi:10.1016/j.jpeds.2015.02.045 ↩
  5. Adamkin DH; Committee on Fetus and Newborn. Postnatal glucose homeostasis in late-preterm and term infants. Pediatrics. 2011;127(3):575-579. doi:10.1542/peds.2010-3851 ↩
  6. 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 ↩
  7. Harding JE, Harris DL, Hegarty JE, Alsweiler JM, McKinlay CJD. An emerging evidence base for the management of neonatal hypoglycaemia. Early Hum Dev. 2017;104:51-56. doi:10.1016/j.earlhumdev.2016.12.009 ↩
  8. Yefet E, Massalha M, Talmon G, et al. Metformin, Maternal Glycemic Control, and Neonatal Hypoglycemia After Antenatal Steroids: A Randomized Clinical Trial. JAMA Netw Open. 2026;9(1):e2552807. doi:10.1001/jamanetworkopen.2025.52807 ↩
  9. Rowan JA, Hague WM, Gao W, Battin MR, Moore MP; MiG Trial Investigators. Metformin versus Insulin for the Treatment of Gestational Diabetes. N Engl J Med. 2008;358(19):2003-2015. doi:10.1056/NEJMoa0707193 ↩
  10. Rowan JA, Rush EC, Obolonkin V, Battin M, Wouldes T, Hague WM. Metformin in gestational diabetes: the offspring follow-up (MiG TOFU): body composition at 2 years of age. Diabetes Care. 2011;34(10):2279-2284. doi:10.2337/dc11-0660 ↩