A mother’s breast milk contains nutrients and immunological benefits important for every newborn, a fact recently confirmed by the U.S. surgeon general and the World Health Organization.

For very low birth weight (VLBW) infants—babies born weighing 3.3 pounds or less—in neonatal intensive care units (NICUs), not consuming breast milk can have potentially devastating consequences.

“In the case of premature babies, they’re not fully developed, their immune systems aren’t complete,” says Eileen Lake, a nursing and health policy professor at the School of Nursing. Breast milk gives the infants “this marvelous natural source of nutrition and an immune boost.”

Despite the known advantages of breast milk for premature babies, not all leave the hospital on a human milk diet. Lake and colleagues, including Diane Spatz, a perinatal nursing and nutrition professor at Penn and director of the Lactation Program at the Children’s Hospital of Philadelphia, wanted to understand why.

In a new paper published in the International Journal of Nursing Studies, based on research funded by the Robert Wood Johnson Foundation, the National Institutes of Health, and Penn, the researchers conclude that in NICUs with better work environments and better-educated nurses, more critically ill infants leave the hospital drinking breast milk. The team looked at data from around 7,000 infants at 97 nursing units nationwide, and surveyed close to 5,600 nurses.

Better work situations—such as having a strong nurse manager and collegial relationships with physicians, a voice in hospital decisions, sufficient resources, and a nursing model driven by nursing care—lead to improved outcomes, the researchers report.

“If you give registered nurses better work environments, they can help fragile newborns get the best nutrition,” Lake says.

Education level also plays a big role: More nurses with bachelor’s degrees on a unit leads to a large percentage of VLBW babies drinking breast milk. Spatz says that’s likely due to critical thinking learned as part of the education process. 

Though the current research has limitations, such as the fact that it accounted for breast milk consumption only at the point of patient discharge and not throughout the weeks-long stay, these findings could guide NICUs across the country, particularly in an era that places such an emphasis on patient-centered care.

“Changing institutional culture to value human milk and breastfeeding is hard,” Spatz says. “It would be great if everyone says this is the wake-up call we needed, but I think we’re going to have to keep chipping away at it.”

A change in the short-term could help these babies in the long-term, she adds.

“Human milk should be viewed as a medical intervention in the NICU,” she says. “Helping a mother to give her baby human milk should be just as important as managing a baby on a ventilator.”