Growth & Development: The Development of Breast Fed Preterm Infants

Several studies of the effect of human milk feeding on the development of preterm infants have been published.

Study by Lucas

The study performed by Lucas involved 300 preterm infants in two groups. 90 infants in group 1 were fed only formula, while 210 in group 2 were given breast milk by NG tube. Feeding progressed as tolerated ( Lucas, 1992 ).

Results

1. Only 35 of the infants who were fed mother's milk (group 2) went home breastfeeding.

2. The average increase in developmental test score at age 7 to 8 years was 7.6 points for the group who were fed their mother's milk (group 2), compared with group 1, as measured by the WISC-R.

3. Of the 210 mothers in group 2 who intended to express maternal breast milk, 17 were not successful.
   1. The mean developmental test score of those 17 children who did not actually receive maternal milk was 94.8.

   2. The mean score of those children whose mothers never intended to feed human milk (group 1) was 92.8.

   3. The mean score of the 193 infants who did received some maternal milk was 103.7.

4. If the 35 children in group 2 who received mother's breast milk after they went home were excluded from the group, the difference in scores was still 7.5 points.

Conclusions

1. The main improvement in developmental tests scores appears to have come from feeding premature infants maternal breast milk while in the hospital in the first couple of weeks of life.

2. This difference persisted when socioeconomic class and mother's education was factored into the statistical analysis.

3. Those children who did not receive breast milk, despite their mother's intention to breast feed, had WISC-R test scores that were very similar to those of children whose mothers never intended to breast feed. This further supports the theory that components of human breast milk do help to improve the cognitive development of premature infants.

Study by Feldman

Feldman and Eidelman reported the effects of different amounts of human milk feeding on developmental test scores of preterm Israeli infants at 6 months corrected age. 86 infants with a mean birth weight of 1298 gms and a mean gestational age of 30.5 weeks were divided into 3 groups by the amount of breast milk the infant received during their initial hospitalization (<25% of nutrition, 25-50% of nutrition, and >75% of nutrition). They also compared the mother infant interactions among the three groups during a 10 minute videotaped period of maternal infant interaction at 37 weeks corrected gestation.

* p < 0.05 among all groups
** p < 0.05 when a is compared to b or c with no difference between b and c
*** p < 0.01 when a is compared to b or c with no difference between b and c

Conclusions

1. The Israeli infants who received the most breast milk had higher mental and motor development scores at 6 months corrected age.
2. Mothers who provided the most breast milk spent more time in affectionate touch and less time talking to their infants at 37 weeks gestation.
3. Mothers who provided the least breast milk spent less time in affectionate touch and more time talking to their infants at 37 weeks gestation.
4. Infants who received the highest amount of breast milk and high levels of maternal touch had the highest mental developmental index score at 6 months.
5. Whether this difference persists as the children grow older remains to be seen ( Feldman, 2003 ).

Study by Vohr

Vohr and coworkers at 12 neonatal intensive care units in the United States prospectively enrolled 1,154 very low birth weight premature infants in the Glutamine Trial from 1999 to 2001 through the National Institute of Child Health and Human Development Neonatal Research Network. Nutritional intake was collected on all infants during hospitalization. The growth and development of these infants were monitored longitudinally. Excluding infants who died in the NICU or before 30 months of age, 773 (82%) of the 939 infants had developmental evaluation at 30 months of age (2 and 1/2 years). The Bayley Scales of Infant Development II was used for developmental testing.

Of the 773 infants evaluated at 30 months of age, 593(77%) received some breast milk in the NICU and 180(23%) received no breast milk. There was a statistically significant difference in family characteristics between the infants who received any breast milk and those who received no breast milk. These differences are summarized in the table below.

Multiple regression analysis of the Bayley developmental test score using amount of breast milk ingested in 10 ml/Kg/day units and adjusting for the variables of maternal age, education, marital status, race, infant gestation, gender, infant sepsis, intraventricular hemorrhage, periventricular leukomalacia, necrotiziing enterocolitis, oxygen use at 36 weeks gestation, and weight <10 %tile at 18 months of age was performed. For every 10 ml/kg/day of breast milk ingested, the MDI (mental developmental scale) score increased by a estimated 0.59 points the PDI (motor developmental scale) increased by 0.56 points and the Behavioral scale increased by 0.99 points. The average MDI of the infants who received no breast milk was 76.5 (normal is 100) so an infant who received 110 ml/kg/day of breast milk during hospitalization would have an average MDI score of 76.5 + 11(.59) or 83. Any amount of breast milk was found to be helpful and the more the better ( Vohr, 2007 ).

What should we understand about these studies?

1. The original study by Lucas compared infants fed maternal milk to infants fed formula that was designed for term infants. Changes in formula to make them more appropriate for preterm infants have occurred since this study was undertaken.
2. The study by Vohr confirms the role of breast milk in improving the development outcomes of very low birthweight infants born at the beginning of the 21st century.
3. As in the studies of the effect of breastfeeding on development of infants born at term, many other factors including maternal education, intelligence, severity of illness at birth, and degree of prematurity are also factors in the final developmental outcome of children born prematurely. However, all mothers who are at risk of delivering or have delivered a premature infants must receive counseling about benefits of breast milk feeding for their infant's developmental outcome along with the other benefits of breast milk.