New study shows not all breast milk protects against NEC

August 8, 2023
Mom breastfeeding baby
Not all breast milk protects against NEC, new study shows

Not all breastmilk is created equal.

At least that’s what Dr. Timothy Hand, a March of Dimes researcher at the University of Pittsburgh, found when studying the link between breast milk and a life-threatening prematurity-related condition called necrotizing enterocolitis (NEC).

The findings were recently published in the Journal of Experimental Medicine. The report’s lead author Dr. Chelseá B. Johnson-Hence and Dr. Hand show that each mother passes on a unique set of antibodies to her baby. Unfortunately, some mothers’ breastmilk is low in antibodies that protect against NEC. 

“This means that if a baby’s parent happens to lack particular antibodies — such as those that fend off NEC, they’re never going to receive that immunity,” Dr. Hand said. “This could help explain why some babies get NEC and others don’t.”

In an interview with March of Dimes, Dr. Hand said the same would be true for a range of other illnesses. A baby’s protection is significantly impacted by the antibodies delivered from breastmilk.

Dr. Hand’s finding opens the door to the development of antibodies or therapeutics that could be added to breast milk or formula to boost immunity against NEC. 

The level of Immunoglobulin A (IgA) antibodies that protect against NEC vary across women. Some women pass on high levels of IgA, and others pass on low, or non-existent, levels through breastmilk. The babies that don’t receive enough of the right level of IgA are at risk of developing NEC. This finding sheds light on the confusing scenario where, despite consuming breast milk, which has been shown to be protective against NEC, some babies still develop it.

The composition of antibodies in a woman’s breastmilk, Dr. Hand said, depends on that woman’s life experiences, illnesses, infections, gut microbiome composition and other factors. 

“It makes perfect sense that breast milk antibodies would reflect that variability,” he said.

NEC, which occurs when a baby’s intestines become inflamed and infected, is a rare condition for babies overall, but a common one for babies born prior to 33-weeks gestation. 

The illness has previously been shown to be two to four times more common in formula-fed babies than breastmilk-fed babies. Because babies with NEC are usually underdeveloped and cannot take milk from the breast, they are fed breastmilk through a nasal tube; that milk is either expressed from the mother’s breast or is donor breast milk. 

Previous research has shown that immune cells called B cells, or B lymphocytes, travel from a mother’s intestine to her mammary glands during pregnancy and begin making antibodies to offer protection to her baby via breastmilk. 

Dr. Hand’s earlier studies showed that in healthy babies, bacteria associated with NEC are bound up by IgA in the intestine, effectively disarming the bacteria. In babies with NEC, the bacteria are unbound and free to cause harm. 

This most recent study also sheds light on the mother’s immune process during pregnancy in order to protect her baby. 

Interestingly, Dr. Hand found that the breast milk of women who deliver preterm contained the same amount - and diversity - of antibodies as the milk of mothers who did not deliver preterm. This means that the B cells from the mother’s intestine likely travel to the mammary glands throughout pregnancy – not just in the third trimester, as had been suggested in other studies.

Dr. Hand also hypothesized that these B cells that travel from the mother’s intestine to the mammary gland and make antibodies for breast milk may actually be doing a round trip - back and forth from the intestine to the mammary glands and back. This journey takes place between a woman’s pregnancies and breastfeeding periods.

“It’s fascinating because the mother may be constantly moving her best immune cells from her intestine to the mammary glands to protect her infant,” Dr. Hand told MoD.

The study’s findings come from analysis of 101 donor breast milk samples from the Human Milk Science Institute and Biobank in Pittsburgh and Mommy’s Milk Human Milk Research Biorepository in San Diego. The study revealed that donor milk - which is sterilized before being given to premature babies in order to kill bacteria - has reduced antibody levels as a result of the sterilization.

However, because it’s not known exactly what level of antibodies protect against NEC, it’s unclear if infants who receive donor milk get enough IgA to offer reliable immunity from NEC. Another unknown is whether all – or only some - babies are born with the bacteria that can lead to NEC.

Dr. Hand is pursuing a few immediate next steps from this work.

First is to replicate the study’s findings in a larger validation study containing milk from a more diverse group of women - including women from around the world with a range of health profiles, including ones that could compromise their gut microbiome, like Irritable Bowel Syndrome (IBS).

Second is to identify the specific bacteria species associated with NEC. This would allow scientists to build therapeutic antibodies that could be added to formula or breast milk to boost immunity.

Dr. Hand’s insights from this study amplify the work of March of Dimes Stanford Prematurity Research Center scientist Dr. Nima Aghaeepour. Earlier this year, Dr. Aghaeepour’s group found that women with stronger immune systems (as measured by routine laboratory tests) give birth to newborns that are at decreased risk of NEC.