Should Every Newborn Be Tested for G6PD Deficiency? What Two New York Hospitals Learned

A family guide to the Mount Sinai study by Dalldorf and colleagues and the Brooklyn safety-net hospital project by Sriraman and colleagues, both published in 2026

Two New York City hospitals began testing every newborn in their nurseries for G6PD deficiency, a common inherited condition that can make jaundice more severe. Babies who had it needed extra jaundice care more often, and choosing whom to test by family background would have missed many of them. The studies show that testing every baby is practical, although they could not show whether it prevents the rare brain injury that severe jaundice can cause.

Most parents first hear about bilirubin when their baby's skin or eyes turn a little yellow in the first days of life. This newborn jaundice is common and usually harmless, and nurseries are well practised at watching it. Some babies, though, have a hidden reason for their jaundice to climb faster than expected. This article explains one of those reasons, G6PD deficiency, and what two recent studies tell families about testing for it.

What G6PD deficiency is and why it matters for jaundice

G6PD stands for glucose-6-phosphate dehydrogenase, an enzyme (a chemical helper) that protects red blood cells from damage. Some people inherit a gene that makes too little of it. Most never know, because they feel perfectly well. But certain triggers, such as eating fava beans, taking some medicines or having an infection, can make their red blood cells break apart quickly [1]. About 400 million people worldwide are thought to have the condition [2]. The gene sits on the X chromosome, so boys are affected more often and more clearly than girls. Girls have two X chromosomes, so a girl who inherits the gene usually also has a working copy, and she often has "in-between" levels [3].

When red blood cells break down in a newborn, they release bilirubin, the yellow substance that causes jaundice. Normally a baby's liver clears it. In babies with G6PD deficiency, bilirubin can build up quickly. Very rarely, very high bilirubin can damage the brain, a condition called kernicterus. Researchers have long noted that G6PD deficiency is a hidden risk factor in many of these rare cases [4].

How doctors used to decide which babies to test

For many years, most US babies were not tested for G6PD deficiency at all. A review of 125 children with kernicterus in a US registry found that the main root cause was a failure of the health system to spot at-risk babies and to treat their rising jaundice in time [5]. Black babies are overrepresented: they make up about 14% of US births but more than 25% of kernicterus cases [6]. Among African American babies with kernicterus, G6PD deficiency has been found in roughly 6 out of 10 [7]. This is a striking pattern, because African American babies are, overall, less likely than other babies to develop high jaundice levels. In other words, the babies at greatest risk were often the ones least likely to be flagged by a quick look at the usual warning signs. Other countries acted earlier. In 1989, World Health Organization experts recommended testing newborns, and teaching parents about the condition, in places where it is common [8]. Greece, for example, tested more than a million newborns between 1977 and 1989 [9]. In the United States, testing was generally reserved for babies already being treated for jaundice whose family background suggested a risk, or whose jaundice did not improve with treatment, and doctors had not agreed on a national approach [10].

Two recent changes moved things forward. The 2022 national jaundice guideline of the American Academy of Pediatrics, as described in the studies, treats G6PD deficiency as a reason to start light treatment sooner and no longer uses race to judge a baby's risk [11]. In New York, a law enacted in December 2021, the Brody James Bill, required testing for babies judged to be at higher risk because of their medical signs or family ancestry. Pennsylvania and Washington, DC, test all newborns [12]. Some New York hospitals decided to go further and test every baby, regardless of background.

What the two hospitals did

The first study comes from Mount Sinai Hospital, a large teaching hospital in Manhattan. Its team had earlier described how they set up testing for every newborn [13]. In this study, Dalldorf and colleagues looked back at the medical records of 5,470 babies tested in the program's first year, from June 2022 to June 2023 [14]. They compared babies with normal, in-between and low enzyme levels, and checked how many affected babies the state's "at-risk" rule would have caught.

The second study comes from NYC Health + Hospitals/Kings County, a public "safety-net" hospital in Brooklyn that serves a mostly African American and African Caribbean community. There, about 87 in every 100 mothers were recorded as African American. Sriraman and colleagues ran a quality-improvement project, meaning a planned effort to change how a hospital works and to track whether the change sticks [15]. The test was added automatically to the standard newborn orders. It used a few drops of blood taken at the same time as the routine jaundice blood test, so babies needed no extra needle. Parents were told about the test and could say no. Results took 5 to 7 days, so most arrived after the family had gone home, and nursery doctors made their decisions without knowing them. The Brooklyn team later compared its findings with the Mount Sinai study and found that they agreed.

What the studies found

At Mount Sinai, about 17 in every 1,000 babies had G6PD deficiency (91 babies), and about 3 in every 100 boys. Babies whose mothers were Black were five times as likely to be affected. But the condition was found across many backgrounds. About one in five affected babies had a parent who identified as Puerto Rican or Dominican, and about one in eight had parents who identified as White and Ashkenazi Jewish. The researchers estimated that testing only babies who fit the state's "at-risk" description would have missed up to 44 in every 100 affected babies before they went home. Family background is also an unreliable guide in practice, because hospital records of race and ethnicity are often wrong [16].

At the Brooklyn hospital, testing went from no babies to a steady average of about 81 in every 100 babies each month, which beat the team's goal of 75. Staff did not report extra workload. Of 580 babies tested, 52 (about 9 in 100) had low levels, including about 15 in 100 boys and 2 in 100 girls. The two hospitals used different cut-off points and serve very different communities, so their numbers should not be compared directly.

Affected babies needed more jaundice care. At Mount Sinai they were more likely to receive light treatment (phototherapy) before going home, and more likely to come back to hospital for it. Among babies whose follow-up care was at Mount Sinai, about 6 in 100 affected babies were readmitted, compared with about 1 in 100 unaffected babies. In Brooklyn, 10 of the 52 affected babies reached high bilirubin levels, compared with 12 of the 528 babies who did not screen positive. Three affected babies and five babies who did not screen positive were readmitted for light treatment, which is too few to draw firm conclusions. Reassuringly, no baby in either study needed an exchange transfusion, an emergency blood-replacement treatment for very severe jaundice. Neither study was designed to count brain injury from jaundice, which is now very rare.

What this means for your family

If your hospital tests for G6PD deficiency and your baby's result is low, this is useful information, not a cause for alarm. Your baby's care team can watch bilirubin more closely and start light treatment at a lower level, as the national guideline advises [11]. You may be referred to a blood specialist (hematologist) to confirm the result and to learn which foods and medicines to avoid. In Brooklyn, only 62 of every 100 families who were referred made it to that appointment, so keeping it matters. If results come back after you leave hospital, ask who will call you and when. An "in-between" result also deserves follow-up, because a few of these babies turn out to be deficient on retesting. Girls can have in-between levels simply because they carry one affected copy and one working copy of the gene, so a specialist can help you understand what your daughter's result means.

If your hospital does not test every baby, you can still ask about G6PD testing, especially if relatives have the condition or your baby's jaundice is rising quickly. Watching for jaundice after discharge and keeping follow-up visits remain the most important steps for every family.

What researchers are working on next

Both studies came from single hospitals and could not show whether testing every baby prevents the rare cases of brain injury. Researchers have begun comparing what testing everyone, testing only "at-risk" babies and usual care each find [12]. They are also working on faster tests that give answers before a baby goes home, on agreed cut-off levels, and on better ways to make sure families get their results and follow-up care. Some teams are studying breath tests that measure how fast red blood cells are breaking down [17]. In[Neo]Sight has also written about inherited causes of newborn jaundice.

The takeaway

Testing every newborn for G6PD deficiency proved practical in two very different New York hospitals (in Brooklyn it needed no extra needle) and found many affected babies whom an ancestry-based approach would have missed. Those babies needed more jaundice care, and knowing early helps doctors and families keep a closer eye on them. Whether universal testing prevents the rarest and most serious harms is the question researchers still need to answer.

References

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