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
Characteristics of Lucas's comparative study of 300 preterm infants
||Group 1, n=90
no mother's milk
|Group 2, n=210
|mean birth weight
|mean gestational age
|% ventilated > 5 days
|% in social class 1 or 2
|% of mothers with higher educ.
|mean WISC-R score (age 7 to 8)
- Only 35 of the infants who were fed
mother's milk (group 2) went home breastfeeding.
- 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.
- Of the 210 mothers in group 2 who
intended to express maternal breast milk, 17 were not
- The mean developmental test
score of those 17 children who did not actually receive
maternal milk was 94.8.
- The mean score of those children whose mothers never intended
to feed human milk (group 1) was 92.8.
- The mean score of the 193 infants who did received
some maternal milk was 103.7.
- 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.
- 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.
- This difference persisted when
socioeconomic class and mother's education was
factored into the statistical analysis.
- 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
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
Characteristics of the infants in the three groups
|| > 75% of Nutrition as Breast Milk(a) N=34
|| 25-75% of Nutrition as Breast Milk(b) N=21
|| < 25% of Nutrition as Breast Milk(c) N=31
||1302 ± 320 gm
||1298 ± 309 gm
||1354 ± 388 gm
||30.8 ± 2.4 wks
||29.9 ± 3.3 wks
||31.1 ± 3.5 wks
||28.6 ± 5.3 yrs
||29.1 ± 6.1 yrs
||29.9 ± 5.8 yrs
||14.7 ± 2.0 yrs
||13.6 ± 3.1 yrs
||14.0 ± 2.0 yrs
|Infant Age at First Breast Milk
||4.3 ± 1.7 days
||5.3 ± 2.3 days
||6.7 ± 4.2 days
|Mean % of Nutrition as Breast Milk
||84% ± 23%
||38% ± 22%
||11% ± 9%
||4.4 ± 4.5% of time
||7.2 ± 6.7% of time
||9.9 ± 8.5% of time
|Maternal Affection touch*
||21.5 ± 11.8% of time
||17.8 ± 9.0% of time
||13.1 ± 9.5% of time
|6 Month Bayley Mental Development Index**
||94.2 ± 8.7
||91.7 ± 7.2
||90.5 ± 8.5
|6 Month Bayley Psychomotor Development Index***
||85.7 ± 11.5
||78.6 ± 12.6
||78.0 ± 11.4
* 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
- The Israeli infants who received the most breast milk had higher mental
and motor development scores at 6 months corrected age.
- Mothers who provided the most breast milk spent more time in affectionate
touch and less time talking to their infants at 37 weeks gestation.
- Mothers who provided the least breast milk spent less time in affectionate
touch and more time talking to their infants at 37 weeks gestation.
- 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.
- Whether this difference persists as the children grow older remains to be
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
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.
Characteristics of Infants and Families
||Received any breast milk (%)
||Did not receive breast milk (%)
|Number of infants
|Education < H.S.
|Race/ethnicity - black
|Income < $20,000
|Gestational age (mean)
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 (
What should we understand about these studies?
- 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.
- 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.
- 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.