Researchers compared two types of nutrition for babies born very early (before 29 weeks of pregnancy). Some babies received donated breast milk from other mothers, while others received special formula designed for premature infants. By age 2, both groups of babies had similar growth and body measurements. However, babies who received donated breast milk gained weight a bit faster after leaving the hospital. The study suggests that donated breast milk works just as well as special formula for helping extremely premature babies grow healthy.

The Quick Take

  • What they studied: Whether premature babies grow better when fed donated breast milk compared to special premature infant formula during their first weeks of life
  • Who participated: 376 babies born very early (before 29 weeks of pregnancy or weighing less than 1000 grams) from 15 hospitals across the United States between 2012 and 2019. About half received donated breast milk and half received formula.
  • Key finding: At age 2, babies in both groups had nearly identical growth measurements. Babies fed donated breast milk gained weight slightly faster between hospital discharge and age 2 (a difference that was statistically significant but small in practical terms).
  • What it means for you: If you have a baby born very early, donated breast milk appears to be a safe and effective alternative to special formula. This is encouraging news for families who want breast milk but cannot produce enough of their own. Talk with your medical team about what’s best for your specific situation.

The Research Details

This was a randomized controlled trial, which is one of the strongest types of medical research. Researchers randomly assigned 483 extremely premature babies to receive either donated breast milk or special premature formula. Neither the parents nor the doctors knew which babies were getting which type of nutrition (called a “double-blind” study), which helps prevent bias. The babies were followed until they reached 2 years old (adjusted for how early they were born), and researchers measured their weight, length, and body mass index (BMI).

The study took place at 15 major medical centers across the United States from 2012 to 2019. Babies were eligible if they were born before 29 weeks of pregnancy or weighed less than 1000 grams (about 2.2 pounds) at birth. These are extremely premature babies who need special care in the hospital. The researchers wanted to see if there would be any differences in how well these two groups grew by age 2.

Premature babies have special nutritional needs because their bodies aren’t fully developed yet. Breast milk has many benefits, but not all mothers can produce enough milk for their premature babies. Donated breast milk from other mothers could be a good option, but doctors needed to know if it helps babies grow as well as special formula designed just for premature infants. This study provides important evidence to help doctors and families make the best feeding choices.

This study is high quality because it used random assignment (like flipping a coin to decide which babies got which nutrition), was double-blind (neither parents nor doctors knew which babies got which type), and followed babies for 2 years. However, 107 babies who started the study didn’t come back for the 2-year check-up, which is a limitation. The study was conducted at major medical centers with experienced doctors, which increases confidence in the results.

What the Results Show

The main finding was that at 2 years old, babies in both groups had very similar body measurements. The BMI Z-score (a way doctors measure if a baby is a healthy weight for their size) was nearly identical: 0.21 for babies who received donated breast milk and 0.23 for babies who received formula. These numbers are so close that they’re considered the same.

However, the researchers noticed something interesting about how the babies grew between leaving the hospital and age 2. Babies who received donated breast milk gained weight a bit faster during this time period. The weight Z-score increase was 1.04 for the donated milk group compared to 0.73 for the formula group. While this difference was statistically significant (meaning it’s unlikely to be due to chance), the practical difference is small—both groups ended up at healthy weights.

This pattern suggests that donated breast milk may help premature babies catch up in weight slightly faster after they leave the hospital, but by age 2, both groups have caught up to similar growth levels.

The study found that the overall growth patterns were similar between the two groups. Length and other body measurements at the 2-year follow-up were comparable. The researchers also noted that 376 out of 483 babies (about 78%) completed the study and came back for measurements at 2 years, which is a good follow-up rate for this type of long-term study.

Previous research has shown that breast milk has many benefits for all babies, including premature ones. This study adds important information by showing that donated breast milk (from other mothers) works just as well as special formula for growth in extremely premature babies. This supports the idea that breast milk is valuable even when it comes from donors, not just from the baby’s own mother.

About 22% of babies who started the study didn’t return for the 2-year check-up, which could have affected the results if those babies were different from the ones who did return. The study only looked at babies born before 29 weeks or weighing less than 1000 grams, so the results may not apply to babies born slightly later or weighing more. The study was conducted between 2012 and 2019, so feeding practices and donor milk availability may have changed since then.

The Bottom Line

For extremely premature babies, donated breast milk appears to be a safe and effective alternative to special premature formula (moderate to high confidence). If a mother cannot produce enough of her own breast milk, donated breast milk is worth considering. Parents should work with their medical team to decide what’s best for their baby, as individual circumstances vary.

This research is most relevant to parents of babies born very early (before 29 weeks of pregnancy), neonatal intensive care unit (NICU) doctors and nurses, and hospital administrators deciding on feeding policies. It’s less relevant to parents of babies born closer to their due date or full-term babies. If you have a baby in the NICU, talk with your medical team about whether donated breast milk is available and appropriate for your situation.

The study measured growth at 2 years old (adjusted for prematurity). Parents shouldn’t expect to see major differences in growth between donated milk and formula in the short term. The key is that by age 2, both groups had caught up to similar healthy growth patterns. Benefits may take weeks to months to become apparent.

Want to Apply This Research?

  • Track your premature baby’s weight gain and growth measurements at regular doctor visits (typically monthly for the first year, then every 3 months). Record the actual measurements and the Z-scores your doctor provides to monitor catch-up growth over time.
  • If you’re feeding a premature baby, discuss with your medical team whether donated breast milk is available at your hospital. If you’re producing your own breast milk, work with a lactation consultant to maximize your supply. Log feeding type and amounts in your app to track consistency and identify any patterns.
  • Set reminders for regular growth check-ups and record measurements in your app. Compare your baby’s growth curve over time rather than focusing on single measurements. By 2 years old (adjusted for prematurity), your baby should be following a healthy growth pattern regardless of whether they received donated milk or formula.

This research summary is for educational purposes only and should not replace professional medical advice. Feeding decisions for premature babies should always be made in consultation with your pediatrician or neonatologist, who understands your baby’s specific medical needs and circumstances. The findings apply specifically to extremely premature babies (born before 29 weeks or weighing less than 1000 grams) and may not apply to other infants. Always follow your medical team’s recommendations for your individual baby’s care.