Everything to Know About Donor Breast Milk

Milk storage bags lined up with a breast pump on side.

What is donor breast milk?

Donor breast milk is human milk that is used as a substitute or supplement for mothers’ own milk. Premature babies (born less than 37 weeks’ gestation) are the largest group of infants who receive donor breast milk, but donor human milk is increasingly being used as a supplement for breastfeeding full term babies in neonatal intensive care units (NICUs) and newborn nurseries.  

Why is donor breast milk preferred to supplement breastfeeding over infant formula?

There are many benefits of supplementing full term and preterm babies with donor human milk. Breast milk bolsters the immune system to help babies fight infections, helps to form a healthy and diverse microbiome (population of “good” bacteria in the gut), and is associated with improved vision and developmental outcomes.

Donor breast milk is also life-saving for premature, small, and fragile babies, as it helps to prevent a very serious bowel condition called necrotizing enterocolitis (NEC). NEC is the most common cause of death in premature infants who are older than 2 weeks. Preemies who receive any infant formula are at a much higher risk of NEC than those who are on 100% human milk diets. Prior to donor breast milk availability, 10-15% of extremely premature babies in the U.S. developed NEC every year, and many died from it. Thanks to the widespread use of donor breast milk, the rate of NEC in preemies has dropped down to about 1-2% in recent years.

Is donor breast milk safe?

The majority of donor human milk that is distributed in the U.S. comes from human milk banks like mothers’ milk bank (a nonprofit milk bank). The first priority for breastfeeding women who donate to milk banks is go through a screening process, including blood tests, by their healthcare provider. They are tested for many infectious diseases, including HIV, syphilis, and hepatitis B&C, and carefully screened to make sure they are not on any unsafe medications, do not use illegal drugs, and are in overall good health. Human milk that is donated to milk banks is pasteurized (heated to very high temperatures) to kill off harmful bacteria and other organisms.

The rest of the donor breast milk we use in NICUs is “shelf-stable” human milk which is sterilized prior to being distributed and given to babies. This sterilized milk is packaged and kept at room temperature. Like human milk bank donors, the mothers who donate their milk to entities that process shelf-stable milk are carefully screened for infections, health conditions, and medications and supplements that are not compatible with breastfeeding.

What about informal, or “peer-to-peer,” breast milk sharing?

Throughout history babies have received breast milk from other women. “Wet nurses” were commonly used until the beginning of the 20th century when homemade infant formula became the substitute or supplement of choice for mothers’ breast milk. 

Informal, or “peer-to-peer,” human milk sharing has gained popularity in recent years. We recommend that parents use caution in giving their babies pumped milk that has been donated by family members, friends, and acquaintances, and to totally avoid purchasing donated milk that does not come from a human milk bank. This is because pumped milk can easily become contaminated if it is not stored correctly and/or good hygiene is not used with milk collection. Previous studies have also shown that a significant percentage of breast milk that one might find for sale on the internet is adulterated with cow’s milk, which is not an appropriate source of nutrition for infants. 

Premature babies and former preemies should only receive donor milk that comes from a human milk bank or a reputable distributor of “shelf-stable” milk, due to the high risks of bacterial contamination and infection from breast milk that is informally shared. 

Does donor breast milk have a different nutritional profile than mothers’ own milk?

Research has shown that pasteurized donor human milk has lower levels of protein, antibodies, digestive enzymes, and “good” bacteria than mothers’ own milk. Because of this, I am a huge advocate of mixing in a little bit of mothers’ own milk to every donor milk feed, if possible.  Babies who do receive a lot of donor milk in the NICU need to have their growth carefully monitored. Sometimes extra fortification needs to be added to this milk to provide extra calories, protein, and minerals for healthy bone growth. 

Do you have any advice on combination feeding using donor milk in the NICU?

As we’ve previously discussed, we recommend that mothers of preemies in the NICU pump as much as they are able so that their babies get all of the benefits of their own milk. However, the reality is that it can be difficult to maintain a full milk supply if you are exclusively pumping and/or are separated from your baby for long stretches of time! Please know that it is okay if your baby needs to be supplemented with extra breast milk. As we’ve discussed, donor human milk is a very safe option for your baby to get. Your own milk will be given to your baby preferentially over donor milk. Most babies can tolerate going back and forth between feeds of their mom’s milk and donor milk without a problem, and the two types of milk can also be safely combined into tube feeds or bottles. 

How can I learn more about becoming a breast milk donor?

The first step in becoming a human milk donor is to contact your nearest milk bank to find out about breast milk donation. The Human Milk Banking Association of North America (HMBANA) has a comprehensive directory to help you to find the milk bank that is closest to you. To go to the HMBANA milk bank directory, please follow this link.

About the Author

Jessica Madden, MD, is the Medical Director at Aeroflow BreastpumpsDr. Madden has been a board-certified pediatrician and neonatologist for over 15 years. She's currently on staff in the neonatal intensive care unit (NICU) at Rainbow Babies and Children’s Hospital in Cleveland, OH. She previously worked in the Boston and Cleveland Clinic Children’s Hospitals. In 2018 she started Primrose Newborn Care to provide in-home newborn medicine and lactation support. She also enjoys traveling, yoga, reading, and spending time with her children.

Information provided in blogs should not be used as a substitute for medical care or consultation.