Researchers studied nearly 36,000 extremely premature babies born in hospitals across Africa, Asia, and Latin America to understand how different feeding methods affect their growth. They found that most babies (84%) received at least some breast milk during their hospital stay. Babies fed only formula gained weight slightly faster than those fed breast milk alone or a mix of breast milk and formula. However, all groups lost some weight compared to expected growth patterns. The study suggests that hospitals in developing countries are doing well at providing breast milk to these vulnerable infants, but doctors may need to find better ways to help breast-fed babies gain enough weight while they’re in the hospital.

The Quick Take

  • What they studied: How different types of hospital feeding (breast milk only, breast milk mixed with formula, or formula only) affect weight gain and head growth in extremely premature babies
  • Who participated: 35,843 babies born very early (at 22-29 weeks of pregnancy) or weighing between 401-1500 grams from hospitals in 12 middle-income countries across Africa, Asia, and Latin America between 2018 and 2024
  • Key finding: Babies fed only formula gained weight slightly better than babies fed breast milk alone or a mix, though all groups lost some weight during their hospital stay. The difference was small but measurable—babies on mixed feeding lost about 0.08 units less weight than those on breast milk only
  • What it means for you: If you have a premature baby in the hospital, breast milk is still very important and most hospitals are providing it. However, doctors may need to improve how they add nutrients to breast milk to help these tiny babies grow better. Talk with your medical team about your baby’s specific feeding plan.

The Research Details

This was an observational cohort study, which means researchers watched and recorded what actually happened to babies in hospitals rather than randomly assigning them to different feeding groups. They collected information on 35,843 extremely premature babies from 2018 to 2024 at hospitals that are part of the Vermont Oxford Network in 12 middle-income countries. The babies stayed in the hospital for a median of 50 days (meaning half stayed longer, half shorter).

Researchers measured how much weight babies gained and how much their head grew from birth until they left the hospital. They compared three groups: babies fed only breast milk, babies fed a mix of breast milk with formula or added nutrients (called fortifier), and babies fed only formula. They used special math to account for differences between babies, like how big they were at birth and whether they were smaller than expected for their age.

This type of study is useful because it shows real-world practices in hospitals where these babies are actually born and treated, rather than in controlled research settings. However, because doctors chose which babies got which type of feeding (rather than it being random), the results need careful interpretation.

Understanding how premature babies grow with different feeding methods is crucial because these infants are extremely vulnerable and need proper nutrition to develop normally. Most research on premature baby feeding comes from wealthy countries with different resources and practices. This study fills an important gap by showing what’s actually happening in middle-income countries where most premature babies in the world are born. The findings can help hospitals improve their feeding practices for these fragile infants.

This study has several strengths: it’s large (over 35,000 babies), includes hospitals from multiple countries and continents, and uses real-world data. However, it’s observational rather than experimental, meaning we can’t be completely certain that the feeding method caused the weight differences—other factors could be involved. The researchers tried to account for these other factors statistically, but some unmeasured differences might still exist. The study also doesn’t tell us whether the weight differences matter for babies’ long-term health outcomes.

What the Results Show

The study found that 84% of babies were receiving at least some breast milk when they left the hospital, which is encouraging. Specifically, 34% received only breast milk, 50% received a mix of breast milk with formula or added nutrients, and 16% received only formula.

When measuring weight changes, all three groups lost weight compared to expected growth patterns (measured using z-scores, which compare each baby to standard growth charts). Babies fed only breast milk lost the most weight (1.40 z-score points), babies on mixed feeding lost slightly less (1.32 points), and babies fed only formula lost the least (1.17 points). The difference between the mixed group and formula-only group was small but statistically significant—about 0.15 z-score points.

Head growth, which is also important for brain development, showed very little difference between the three feeding groups. This suggests that the feeding method mainly affected weight gain rather than head growth.

The median hospital stay was 50 days, with some babies staying as short as 37 days and others staying as long as 65 days or more.

When researchers looked at subgroups of babies (divided by birth weight and whether they were smaller than expected), the patterns were similar across different groups. This suggests the findings apply broadly to very premature babies rather than just specific types. The high rate of breast milk use (84%) across these middle-income countries suggests that hospitals are prioritizing breast milk, which is important because breast milk provides immune protection and other benefits that formula cannot.

Previous research, mostly from wealthy countries, has shown that breast milk is beneficial for premature babies’ long-term health, even if weight gain is slower initially. This study confirms that hospitals in developing countries are successfully providing breast milk to most premature babies. However, the finding that formula-fed babies gain weight faster raises questions about whether breast milk alone provides enough nutrients in these hospital settings. The study suggests that the way nutrients are added to breast milk (fortification) may need improvement in middle-income countries.

This study has several important limitations. First, it’s observational, so we can’t prove that feeding method caused the weight differences—babies receiving different feeding types may have differed in other ways that affected growth. Second, the study doesn’t follow babies after they leave the hospital, so we don’t know if the weight differences matter for their long-term health. Third, the study doesn’t measure exactly how much nutrition each baby received, only what type of milk they were fed. Finally, the study doesn’t explain why doctors chose different feeding methods for different babies, which could affect the results.

The Bottom Line

Based on this research, hospitals should continue prioritizing breast milk for premature babies, as 84% of hospitals in this study were already doing. However, doctors should work to improve how they add nutrients to breast milk to help babies gain weight better. Parents should discuss their baby’s specific feeding plan with their medical team, as individual babies may have different needs. The evidence suggests that breast milk is important, but the way it’s supplemented may need adjustment. (Confidence level: Moderate—this is observational data, not a controlled trial)

This research is most relevant to parents of extremely premature babies (born before 29 weeks) or babies weighing less than 1500 grams, especially in middle-income countries. Hospital doctors and nutritionists caring for premature babies should pay attention to these findings. Public health officials in developing countries can use this data to improve feeding guidelines. This research is less directly applicable to full-term babies or babies born in wealthy countries with different resources.

Premature babies typically spend 1-3 months in the hospital. Weight gain patterns develop over weeks, so improvements in feeding practices would likely show benefits within the hospital stay. Long-term effects on health and development may take months or years to become apparent.

Want to Apply This Research?

  • If your baby is hospitalized, track daily weight measurements and head circumference growth (if provided by hospital staff). Record which type of feeding your baby received each day (breast milk only, mixed, or formula only) and note any changes in feeding plan. This helps you see patterns and discuss progress with your medical team.
  • Work with your hospital’s lactation specialist to establish and maintain breast milk production if you plan to breastfeed. Ask your medical team about fortification options and whether your baby’s feeding plan is optimized for growth. Request regular updates on your baby’s growth measurements and discuss any concerns about weight gain.
  • Keep a simple log of feeding type and any growth measurements shared by hospital staff. After discharge, continue tracking your baby’s growth at regular check-ups. Discuss with your pediatrician whether your baby’s growth is catching up to expected patterns. Note any feeding challenges or changes in your baby’s behavior related to feeding.

This research describes what hospitals are currently doing with premature baby feeding in middle-income countries, but it does not provide personalized medical advice. Every premature baby is unique and may have different nutritional needs based on their specific health conditions, birth weight, and medical history. Feeding decisions for hospitalized premature babies should always be made by the medical team caring for your baby, including doctors, nurses, and lactation specialists. This information is for educational purposes and should not replace discussions with your baby’s healthcare providers. If you have concerns about your baby’s growth or feeding, speak directly with your medical team.