Breast milk is important in the NICU because it protects preterm babies from infections and intestinal complications. One challenge is making sure that preterm babies who are fed breast milk get the right amount of nutrition for healthy growth. Our past research shows that the levels of nutrients in breast milk — like protein and fat – differ from one mom to another. Also, each mom’s breast milk changes from day to day. Currently, the nutrients in breast milk are not measured before fortifying it. This means that even when breast milk is fortified, some babies may receive fewer nutrients than they need to grow.
The Nourish Study compares two different ways to fortify breast milk. Our study team measures babies in several ways to compare how these different ways to fortify milk affect their growth and brain development.
We used a device called a Human Milk Analyzer to measure the exact nutrients in mom’s pumped breast milk or in donor milk. We designed the study to see if adding nutrients based on what is actually in mom’s breast milk or donor milk each day provides better nutrition for preterm babies. This process is called individualized fortification.
The Nourish Study enrolled 137 participants from January 2020 to June 2025.
All babies in the Nourish Study received human milk – either mom’s pumped breast milk, donor milk, or both. Mom’s milk was used first, and donor milk was added only if there is not enough mom’s milk. All milk was fortified based on the NICU standard of care.
Each weekday, we took about 1 teaspoon of breast milk. We analyzed some of the milk to find out how much protein, fat, and energy was in it, and froze the rest of it for future research when agreed to.
Babies in the study were randomly assigned, like flipping a coin, into one of two diet groups: the standard group, or the individualized fortification group. Only the research assistants preparing the milk know which group each baby was assigned to. The other researchers and the clinical team do not know.
For babies in the standard group, milk was fortified just like for babies in the NICU who were not in the study. For babies in the individualized group, we may have added extra liquid protein and/or fat to the milk, depending on the results of the milk analysis. After the milk was fortified, it was given to the baby’s nurse to feed the baby.
The Nourish Study prepared the baby’s milk until he/she reached 36 weeks post-menstrual age – about one month before your due date for the pregnancy. After this point, the baby was fed according to clinical routine every day until he/she went home.
Our study carefully tracks each baby to see if the type of fortification makes a difference, from enrollment to 5 years of age. We measured the baby’s weight, length, and head circumference throughout their NICU stay and at each follow-up timepoint. We measured the baby’s body composition (fat and lean mass) with a bioelectrical impedance device (BIA) both in the NICU and the follow-up clinic. We also measured body composition with the PEA POD device in the NICU and are currently measuring it with the BOD POD device at the 5-year visit. To measure brain growth and development, we performed a brain MRI scan on the baby before he/she went home from the NICU, and developmental tests at their follow-up visits.
What are the PEA POD and BOD POD and how do they work?
The PEA POD is like a small isolette with warm air swishing around inside it. The BOD POD is a larger version of it that can be used with ages 3 years and up. These devices use air displacement plethysmography to calculate body density and help us estimate body fat and lean mass percentages.
What is the BIA and how does it work?
The BIA is a small device that has electrodes placed on the hand and foot. They run a weak, painless current through the body, which takes less than 5 minutes.
It is a big milestone when babies are ready to be discharged from the NICU. To figure out which type of fortification is best, we continue to track baby’s growth and development since they’ve gone home. We are asking parents to allow us to stay in touch through the different study timepoints, so that we can check on how the child and family are doing.
We had questionnaires to fill out at 4 months and 12 months corrected age (time from baby’s original due date) that were done online. All of our families have passed this timepoint as of June 2026!
We are also seeing children at 2 years corrected age, during a visit to the Center for Child Development as part of our NICU Follow-up Program. During these visits, we weigh and measure the children and continue to collect body composition information with the BIA. They also complete developmental assessments as part of this visit. We work to coordinate this visit with regular clinic visits for child.
We now see our participants when they turn 5 years old.
