Growth of Breast-Fed and Formula-Fed Infants From 0 to 18 Months: The DARLING Study

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PEDIATRICS

Vol.

89 No.

6 June

1992

1035

Growth

of Breast-Fed

and

Formula-Fed

Infants

From

0 to 18 Months:

The

DARLING

Study

Kathryn

G. Dewey,

PhD;

M. Jane

Heinig,

MS;

Laurie

A. Nommsen,

MS;

Janet

M.

Peerson,

MS;

and

Bo L#{246}nnerdal, PhD

ABSTRACT.

Anthropometric

data

were

collected

monthly

from

birth

to 18 months

as part

of the

Davis

Area

Research

on Lactation,

Infant

Nutrition

and Growth

study,

which

followed

infants

who

were

either

breast-fed

or formula-fed

during

the

first

12 months.

The

two

cohorts

were

matched

for parental

socioeconomic

status,

education,

ethnic

group,

and

anthropometric

character-istics

and

for

infant

sex

and

birth

weight,

and

neither

group

was

given

solid

foods

before

4 months.

While

mean

weight

of formula-fed

infants

remained

at or above

the

National

Center

for

Health

Statistics

median

throughout

the

first

18 months,

mean

weight

of

breast-fed

infants

dropped

below

the

median

beginning

at 6 to

8 months

and

was

significantly

lower

than

that

of the

formula-fed group

between

6 and

18 months.

In contrast,

length and head circumference values were similar

be-tween

groups.

Weight-for-length

z scores

were

signifi-cantly

different

between

4 and

18 months,

suggesting

that

breast-fed

infants

were

leaner.

The

groups

had

sim-ilar weight

gain

during

the first

3 months,

but

breast-fed

infants

gained

less

rapidly

during

the

remainder

of the

first

year:

cumulative

weight

gain

in the

first

12 months

was

0.65 kg less

in the breast-fed

group.

Length

gain

was

similar

between

groups.

These

results

indicate

that

weight

patterns

of breast-fed

infants,

even

in a

popula-tion

of

high

socioeconomic

status,

differ

from

current

reference

data

and

from

those

of

formula-fed

infants.

Thus,

new

growth

charts

based

on breast-fed

infants

are

needed.

Pediatrics

1992;89:1035-1041;

breast-feeding,

for-mula-feeding,

infant-feeding

practices,

growth,

weight,

length,

anthropometry.

ABBREVIATIONS. NCHS, National Center for Health Statistics; DARLING, Davis Area Research on Lactation, Infant Nutrition and Growth.

There

is evidence

from

several

countries,

including

the

US,

Canada,

Australia,

Finland,

Sweden,

and

the

UK,

that

growth

of

breast-fed

infants

deviates

from

current reference data,’7 although

not

all

studies

have

shown

these

differences.8’3

In

general,

breast-fed

infants

tend

to

grow

rapidly

in

the

first

2 to

3

months,

but

they

grow

more

slowly

than

the

US

National

Center

for

Health

Statistics

(NCHS)

stand-ards

thereafter.

The

NCHS

reference

data

for

infants

are

based

on

data

collected

for

the

Fels

Longitudinal

From the Department of Nutrition and Program in International Nutrition,

University of California, Davis.

Received for publication Jul 10, 1991 ;accepted Sep 1 3, 1991.

Reprint requests to (K.G.D.) Dept of Nutrition, University of California, Davis, CA 95616-8669.

PEDIATRICS (ISSN 0031 4005). Copyright © 1992 by the American Acad-emy of Pediatrics.

Study in Yellow Springs, OH, from 1929 to 1975. Of

the

867

infants

in that

study,

the

great

majority

were

exclusively

bottle-fed

or

were

breast-fed

for

a

rela-tively

short

time.

Therefore,

the

NCHS

standards

may

not be appropriate for breast-fed infants.

There

are

other

aspects

of infant

feeding

that

have

changed

since

the

Fels

data

were

collected

which

may

also

account

for

some

of

the

differences

in

growth

patterns

observed

in

recent

studies

of

breast-fed

in-fants.

Two

key

factors

are

the

timing

of introduction

of

solid

foods,

which

has

shown

a

secular

trend

toward

older

ages

in the

past

two

decades,’4

and

the

types

of

infant

formula

used,

which

have

become

more

similar

to

human

milk

as

our

scientific

under-standing

of its composition

has

increased.

Thus,

it is

important

to compare

growth

of breast-fed

infants

to

that

of

infants

fed

modern

infant

formulas

who

are

given

solid

foods

at

a similar

age.

Although

several

recent

studies

have

compared

growth

of

breast-fed

and

formula-fed

infants,3’5’7’

7 most have not

controlled

for

the

age

at which

solid

foods

are

intro-duced,

few

have

included

sufficient

numbers

of

in-fants

who

are

fully

breast-fed

(ie,

no

other

source

of

milk)

beyond

6 months,

and

none

have

used

match-ing

procedures

to

ensure

that

the

two

groups

are

similar

in

parental

socioeconomic

status,

education,

or anthropometric

characteristics.

The

purpose

of the

Davis

Area

Research

on

Lactation,

Infant

Nutrition

and

Growth

(DARLING)

study

was

to

compare

growth

patterns,

nutrient

intake,

morbidity,

and

ac-tivity

patterns

of

matched

cohorts

of breast-fed

and

formula-fed

infants

during

the

first

1 8 months

of life.

This

paper

will

report

growth

data;

previous

publi-cations

have

included

information

on

breast

milk

volume

and

composition,

energy

intake,

morbidity,

and

activity.’82’

Study

Design

METHODS

The DARLING study was designed to follow prospectively 40 to 50 infants in each of two groups: those breast-fed for at least 12 months, and those not breast-fed for more than 3 months. Subjects were generally recruited within the first month of life. Selection criteria were as follows:

1. (a) Breast-fed group: mothers did not plan to feed more than

120 mL/d of other milk or formula throughout the first year.

(b) Formula-fed group: mothers planned not to breast-feed, or to wean the child completely by 3 months of age, and to use iron-fortified cow’s milk-based formula throughout the first year. Mothers who terminated breast-feeding because of per-ceived lactation failure were not eligible.

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2. Mothers did not plan to introduce solid foods before 4 months. 3. Infants were healthy, of normal gestational age (38 to 42 weeks),

and 2500 to 5000 g birth weight.

4. Mothers did not have any chronic illness and were not taking any medication on a regular basis.

To ensure that infants in the formula-fed group would continue to receive formula throughout the first year, each mother in this group was provided with Enfamil with iron to cover the needs of her infant from 6 to 1 2 months of age. No compensation was provided to the breast-fed group.

Stratified matching was used to ensure that the groups would be comparable in parental socioeconomic status, education, ethnic group, and anthropometric characteristics and in infant sex and birth weight. In this procedure, the formula-fed group was matched to the breast-fed group by setting limits on the number of formula-feeding mothers who could be recruited within predefined cate-gories for each of the above variables. Thus, the proportions of subjects in each category were kept similar between groups, rather than matching individual mother/infant pairs on all characteristics.

For the breast-fed group, 92 subjects were recruited; the number remaining in the study at 3, 6, 9, 12, and 18 months was 73, 60, 51, 46, and 44, respectively. Of the 19 mothers who left the study before 3 months (when the first dietary intake records were com-pleted), most did so because they were too busy or the study procedures were inconvenient.18 Only one breast-feeding mother dropped out because of perceived insufficient milk production. Of the 27 mothers who left the study between 3 and 12 months, 12 did so because their infants weaned themselves before 1 2 months, 9 discontinued because the measurements were inconvenient, and 6 dropped out for other reasons. For the formula-fed group, 52 subjects were recruited; the number remaining in the study at 3, 6, 9, 12, and 18 months was 46, 45, 43, 41, and 36, respectively. Of the 6 mothers who left the study before 3 months, 3 did so because they switched to soy formula, 2 did not terminate breast-feeding, and 1 infant had surgery. Of the 5 mothers who dropped out between 3 and 12 months, 1 switched to soy formula, 1 found the study procedures inconvenient, and 3 moved out of the area. In both groups. characteristics of those who left the study at various time points were compared with those of subjects remaining.

Within the breast-fed group, there were only a few minor

differences’9; within the formula-fed group those who dropped out before 3 months had somewhat lower educational level, pregnancy weight gain, and infant birth weight than those who completed the study to I 2 months, but none of these differences were statis-tically significant.

Of the 41 mothers who formula-fed their infants, 1 1 did not breast-feed at all, while 30 partially breast-fed for varying dura-tions: 8 for less than 1 month, 5 for I to 2 months, and 1 7 for 2 to 3 months. Of these 30 who partially breast-fed, nearly all intro-duced formula within the first 2 weeks. Among the 46 mothers who breast-fed throughout the first year of life, 1 8 breast-fed for

12 to 15 months, 10 for 15 to 18 months, 5 for 18 to 24 months,

and

13 for 24 or more months.

Characteristics of the subjects remaining in the study at 12 months are shown in Table 1.Because of the matching procedures, the groups were very similar in maternal age, education, prepreg-nancy percent of ideal body weight, pregnancy weight gain, paren-tal height, parity. ethnicity, socioeconomic status, and infant sex and birth weight. It should be noted that the average educational level of women in both groups was very high: none had less than

TABLE

1. Characteristics of Subjects

Characteristic Breast-Fed

(n=46)

Formula-Fed (n=41)

Maternal age, yr* Maternal education, yr* Prepregnancy % ideal body wt* Pregnancy weight gain, kg* Mean parental height, cm* Parity

(%

primiparous)

Ethnic group (% white, non-Hispanic) Income (% > $30 000/y)

Infant sex (% male) Birth wt, g*

30.5 (4.8) 16.3 (2.0) 100 (1 1)

15.0 (4.8) 173 (5)

39 89

48

50 3652 (530)

30.5 (5.6) 15.6 (2.4) 103 (14)

16.2 (5.5) 171 (7)

37 85

68

46 3602 (452)

*Mean (SD).

a high school education and many had advanced degrees. There was a slightly higher percentage of subjects with family incomes greater than $30 000 per year in the formula-fed group due to the fact that more of these mothers were employed full-time compared with the breast-fed group.

Anthropometry

Birth weight and length were recorded from parents’ records. Home visits were made monthly from 1 to 1 8 months to measure infant weight (on a beam balance, to the nearest 5 g), length (on an infant measuring board, to the nearest 0.3 cm), and head circumference (using a paper insertion tape, to the nearest milli-meter), following standard procedures.22 Measurements were scheduled to coincide with each infant’s ‘month birthday’: 84% were completed within 4 days of this date. When the measurements were made more than 4 days before or after this date, interpolated values were calculated. z Scores for weight-for-age, length-for-age, and weight-for-length were calculated using NCHS reference data.23 Maternal and paternal height (without shoes) were meas-ured to the nearest 0.5 cm, using a steel tape measure and wooden

900 angle against a wall. At each visit, maternal weight was

measured on a portable digital scale accurate to 0.25 kg. Percent of ideal body weight was calculated using the corrected Fogarty tables.24 Measurements were made by four trained assistants whose techniques were standardized according to the procedure described by the World Health Organization.25

Data

Analysis

Data were analyzed using PC-SAS.’6 Rates of weight and length gain were determined by dividing the difference between measure-ments at different time points by the actual length of time between measurements. Comparisons of weight, length, head circumfer-ence, z scores, and growth velocity between breast-fed and for-mula-fed groups were made using a two-factor analysis of variance model with repeated measures across time, treating feeding practice and age as main effects, including a feeding practice by age interaction and nesting a random subject effect within the feeding practice effect.27 Cumulative weight and length gain during the first 1 2 months were compared between groups using Student’s

test.

To compare weight and length values with current reference data, adjusted values were calculated to correct for the relatively

high

birth weights in our population. This was done by obtaining birth weight distribution data for US singleton, white term infants from the Centers for Disease Control and determining weighting factors for each 250-g interval of birth weight. These factors were calculated by dividing the percentage of children in the national survey within each birth weight interval by the percentage of children in our population within the same interval. Each child’s weight and length values were then multiplied by the appropriate weighting factor and adjusted means were calculated.

RESULTS

Data

on

weight

and

length

of

breast-fed

and

for-mula-fed

boys

and

girls

are

shown

in Tables

2 and

3.

Formula-fed infants were

significantly

heavier

than

breast-fed

infants

at

each

month

between

7 and

18

months

among

boys

and

between

6 and

1 8 months

among

girls.

In

contrast,

there

were

no

significant

differences

in

length

between

groups

among

girls,

and

among

boys

the

differences

were

significant

only

at 1, 9, 12,

and

13 months.

The

results

were

the

same

when

only

those

infants

with

complete

measurements

to 1 2 months were considered.

Figures

1 through

4 illustrate

the

mean

adjusted

weights

and

lengths

(weighted

for

birth

weight,

as

described

under

“Methods’)

of boys

and

girls

in both

groups,

with

respect

to

the

NCHS

25th,

50th,

and

75th

percentiles.

Figure

1 illustrates

that

on

average,

formula-fed

boys

remained

above

the

NCHS

median

throughout

the

first

1 2 months,

whereas

breast-fed

boys fell slightly below the NCHS median beginning

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TABLE

2.

W eight

(in Grams) of Br east-Fed and Form ula- Fed Infants from 0 to 18 Months

Age,

mo

Males

Females

Breast-Fed Formula-Fed Breast-Fed Formula-Fed

No. Mean (SD) No. Mean (SD) No. Mean (SD) No. Mean (SD)

0 1 2 3 4 5

6

7 8 9 10 11 12 13 14 15 16 17 18 34 34 34 34 28 28

28

25 25 25 24 24 24 23 23 23 23 22 23

3 800 (530) 23 4754(525) 21 5829(649) 23

6 605 (714) 23 7 177 (838) 23 7 675 (801) 22

8 095 (880)

22

8399(914) 22

8 778 (928) 21 8 990 (953) 21 9325(980) 21 9492(1003) 21 9745(965) 20 10010(1035) 20 10211(1036) 20 10438(1002) 20 10628(1047) 20 10838(987) 19 11098(1058) 19

3 556 (542) 4616(539) 5698(617)

6 499 (669) 7 224 (743) 7 790 (794) 8 292 (873) 8725(917)t 9 158

()t

9 420 (1044)1 9714(10344 10042(11044 10269(12154 10511(12094 10725(11594 10975(12754 11183(13554 11345(13964 11513(14904 39 36 39 39 34 34 34 25 25 25 23 23 23 21 21 20 21 20 21

3 584 (472) 23

4434(491) 19

5305(531) 21

5 941 (622) 23 6 494 (726) 22 6 938 (793) 23 7 303 (876) 23

7733(993) 23

8 020 (1068) 23 8 277 (1079) 22 8539(1177) 21 8772(1174) 21 8946(1193) 21 9390(1191) 20 9655(1183) 20 9948(1322) 20 10148(1257) 17 10414(1335) 18 10680(1332) 17

3 571 (397) 4402 (338)

5295 (429)

5 952 (487) 6 620 (663) 7 181 (674) 7 676 (692)t 8116(735)t

8 436 (663)t 8 791 (7474 9157(8564 9481(8794 9679(9194 9927(8744 10187(9854 10310(1064)t 10596(1106)t 10678(1146) 10865(1139)

*

P

< .05, breast-fed vs formula-fed, within sex.

tP< .01.

:I:P<

.001.

TABLE

3. Length (in C entimeters) of Bre ast-Fe d an d Formula-Fed Infant s from 0 to 18 Months

Age, mo

No.

Males Females

Breast-fed

Mean (SD) No.

Formula-Fed

Mean (SD) No.

Breast-Fed

Mean (SD)

Formula-Fed

No. Mean (SD)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 34 34 34 34 28 28 28 25 25 25 24 24 24 23 23 23 23 22 23 51.9 (2.4) 56.2 (2.2) 59.9 (2.2) 62.6 (2.3) 64.6 (2.5) 66.9 (2.3) 68.3 (2.3) 69.4 (2.4) 70.4(2.2) 71.9 (2.5) 73.5 (2.5) 74.6 (2.7) 75.8(2.7) 77.3 (2.5) 78.2 (2.6) 79.6 (2.8) 80.8(2.7) 81.4 (2.7) 82.4 (2.9) 23 21 23 23 23 22 22 22 22 21 21 21 20 20 20 20 20 19 19 51.3 (1.8) 55.6 (1.8)* 59.1 (1.5) 62.2 (1.5) 64.5 (1.8) 66.7 (2.0) 68.4 (2.0) 69.8 (1.8) 71.2(1.8) 72.9 (1.9)* 73.8 (2.2) 75.3 (2.6) 76.8(2.6) 78.1 (2.8)* 79.0 (3.2) 80.4 (2.9) 81.4(3.0) 82.2 (3.0) 83.3 (3.0) 39 36 39 39 34 34 34 25 25 25 23 23 23 21 21 20 21 20 21 50.8 (2.5) 54.9 (2.1) 58.2 (2.1) 60.9 (2.1) 63.1 (2.2) 64.8 (1.8) 66.2 (2.1) 67.7 (2.1) 69.2(2.5) 70.3 (2.5) 71.6 (2.6) 73.2 (2.7) 74.5(2.7) 76.1 (2.8) 77.6 (2.8) 78.2 (3.0) 80.0(2.8) 81.1 (3.1) 82.2 (2.9) 23 19 21 23 23 23 23 23 23 22 22 21 21 21 20 20 19 18 17 50.3 (2.0) 54.9 (1.6) 58.5 (2.0) 61.1 (1.8) 63.3 (1.4) 65.2 (1.7) 66.9 (1.3) 68.4 (1.4) 69.7 (1.8) 70.9 (1.7) 72.5 (1.9) 73.6 (1.7) 74.6 (2.0) 76.1 (2.0) 76.9 (2.0) 78.1 (1.8) 79.3 (2.1) 80.5 (2.2) 81.4 (2.2)

*P< .05, breast-fed vs formula-fed males.

at

8 months.

The

difference

for

girls

was

more

dra-matic

(Fig

2),

with

the

average

weight

of

breast-fed

girls

dropping

below

the

25th

percentile

at 1 2 months,

while

formula-fed

girls

remained

well

above

the

NCHS

median.

Differences

in

length

between

the

two

groups

were

much

less

evident

(Figs

3 and

4),

with

breast-fed

infants

showing

somewhat

lower

val-ues

only

at

7 to

10 months.

Given

that

the

weight

differences

were

much

greater

than

the

length

differences,

it is not

surprising

that

mean

weight-for-length

z scores

were

consider-ably

lower

in breast-fed

than

in formula-fed

infants.

Figure

5

illustrates

that

the

differences

between

groups

were

significant

between

4 and

1 8 months;

this

was

true

for

both

boys

and

girls.

These

data

suggest

that

the

breast-fed

infants

were

leaner

than

their

formula-fed

counterparts.

In contrast,

Figs

6 and

7 show

that

there

were

no

significant

differences

in

head

circumference

between

groups.

Mean

values

in

both

groups

were

close

to or above

the

75th

percentile

of current

reference

data

during

the

first

1 2 months.28

These

higher-than-average

levels

probably

reflect

the

high

birth

weights

in both

cohorts.

Data

on

1 -month

increments

in

weight

and

2-month

increments

in

length

during

the

first

18

months

are

shown

in

Tables

4 and

5, respectively.

The

repeated

measures

ANOVA

model

indicated

that

weight

gain

of breast-fed

boys

was

significantly

lower

than

that

of

formula-fed

boys;

among

girls,

the

dif-ferences

were

not

significant.

Length

increments

were

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0

0 1 2 3 4 6 6 7 8 9 101112131416161718 AGE (MO)

0 1 2 3 4 6 6 7 8 9 101112131416161718

AGE (MO)

FEMALES

0

0 1 2 3 4 6 6 7 8 9 101112131416161718

AGE (MO) 0 1 2 3 4 6 6 7 8 9 101112131416161718

MALES MALES

60

44

42

40

0

38

36

34

so,’

25th

0 1 2 3 4 5 6 7 8 8 101112131416161718

AGE (MO)

MALES FEMALES

13

12 11 10

a

8

7

6 6 4 3

Fig

1. Mean weight of male breast-fed and formula-fed infants from birth to 18 months, adjusted for birth weight and compared with the 25th, 50th, and 75th National Center for Health Statistics percentiles.

Fig

2. Mean weight of female breast-fed and formula-fed infants from birth to 18 months, adjusted for birth weight and compared with the 25th, 50th, and 75th National Center for Health Statistics percentiles.

0 1 2 3 4 5 6 7 8 9 101112131416161718

AGE (MO)

Fig 3. Mean length of male breast-fed and formula-fed infants from birth to 18 months, adjusted for birth weight and compared with the 25th, 50th, and 75th National Center for Health Statistics percentiles.

Fig

4. Mean length of female breast-fed and formula-fed infants

from birth to 1 8 months, adjusted for birth weight and compared

with the 25th, 50th, and 75th National Center for Health Statistics percentiles.

AGE (MO)

Fig 5. Weight-for-length z scores (mean ± SEM) of breast-fed and formula-fed infants from birth to 18 months.

Fig 6.

Mean head circumference of male breast-fed and

formula-fed infants from birth to 1 8 months, compared with the 25th, 50th, and 75th percentiles of reference data.2’

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FEMALES

0

15*

#{149}0S

21*

0 1 2 3 4 6 6 7 8

a

101112131416161718

AGE (MO)

Fig

7.

Mean

head circumference

of female

breast-fed

and

formula-fed infants

from birth to

18 months, compared with the 25th, 50th, and 75th percentiles of reference data.28

TABLE

4. Weight Increments (Grams per Month) of Breast-Fed and Formula-Fed Infants From 0 to 18 Months

Interval, mo Males Females

Breast-Fed Formula-Fed Breast-Fed Formula-Fed

No. Mean (SD) No. Mean (SD) No. Mean (SD) No. Mean (SD)

0-1 34 981 (362) 21 1053 (258) 36 871 (326) 19 843 (265)

1-2 34 1079 (356) 21 1095 (267) 36 827 (207) 19 920 (270)

2-3 34 747 (238) 23 805 (128) 38 636 (183) 21 650 (300)

3-4 27 593 (205) 23 731 (174) 34 580 (185) 22 664 (301)

4-5 27 485(195) 22 553(162) 34 452(228) 22 536 (141)

5-6 27 423 (201) 22 495 (184) 34 365 (199) 23 510 (228)

6-7 25 322 (202) 22 434 (270) 25 361 (163) 23 449 (184)

7-8 25 374 (209) 21 389 (243) 25 288 (166) 23 309 (200)

8-9 25 216(170) 20 324(188) 25 247(239) 22 366 (279)

9-10 24 284 (217) 21 306 (194) 23 319 (227) 21 345 (304)

10-11 24 165 (165) 21 346 (225) 23 232 (205) 20 248 (244)

11-12 24 263(181) 20 249(197) 23 190(221) 21 210(245)

12-13 23 229 (163) 19 227 (231) 21 286 (279) 20 289 (278)

13-14 23 201 (211) 20 231 (328) 21 276 (198) 19 251 (281)

14-15 23 211 (205) 20 248 (414) 20 295 (211) 19 182 (224)

15-16 23 204(162) 20 215(232) 20 202(176) 17 123 (249)

16-17 22 245(259) 19 178(268) 20 305(199) 16 170 (220)

17-18 22 279 (266) 18 211 (221) 19 226 (242) 17 238 (170)

Repeated

measures

analysis

of

variance showed a significant difference between breast-fed and

formula-fed males at all ages (P < .01); the differences were not significant for females.

not

significantly

different

between

groups

for

either

boys

or girls.

Three-month

increments

in weight

and

length

(with

the

sexes

combined;

data

not

shown)

were

also

compared:

weight

gain

was

similar

during

the

first

3 months,

but

breast-fed

infants

gained

sig-nificantly

less

weight

than

formula-fed

infants

at 3 to

6,

6 to 9, and

9 to 1 2 months.

In contrast,

length

gain

was

not

significantly

different

between

groups

during

any

of these

intervals.

Cumulative

weight

gain

during

the

first

year

of life

was

significantly

different

between

breast-fed

and

formula-fed

infants:

the

difference

was

0.65

kg

in

both

boys

and

girls.

Cumulative

length

gain

from

birth

to

1 2

months

differed

significantly

between

breast-fed

and

formula-fed

boys

(23.8

± 2.8

[SD]

vs

25.4

±

2.8

cm;

P

<

.05),

but

not

between

breast-fed

and

formula-fed

girls

(23.9

± 2.4

vs 24.1

± 2.8

cm;

P

>

.10).

DISCUSSION

The

results

of

this

study

indicate

that

growth

pat-tents

of breast-fed

infants

differ

not

only

from

current

reference

data,

but

also

from

growth

of

infants

fed

modern

infant

formulas

who

are

given

solid

foods

no

earlier

than

4 months

and

are

similar

with

respect

to

parental

characteristics

and

infant

birth

weight.

Dif-ferences

in weight

were

the

most

pronounced,

partic-ularly

among

girls,

whereas

length

of breast-fed

and

formula-fed

infants

was

generally

similar

and

there

were

no

differences

in

head

circumference.

These

results

suggest

that

breast-fed

infants

are

generally

leaner

than

formula-fed

infants:

our

data

indicated

significant

differences

in

weight-for-length

between

4 and

1 8 months,

which

is consistent

with

differences

in skinfold

measurements

observed

at the

same

time

points

(unpublished

data).

It should

be noted

that

the

subjects

in this

study

were

deliberately

not

a random

or

representative

sample

of

breast-feeding

and

for-mula-feeding

mothers

and

infants:

the

average

edu-cational

level

in both

groups

was

very

high

and

the

majority

were

of relatively

high

socioeconomic

status.

Thus,

we

consider

the

growth

patterns

of the

breast-fed

cohort

to

represent

optimal

environmental

con-ditions;

infants

in less-protected

environments

might

show

an

even

greater

deviation

from

current

refer-ence

data.

Interestingly,

differences

in weight

were

most

evi-dent

during

the

second

6 months

of

life,

after

the

introduction

of

complementary

foods.

We

have

shown

elsewhere

that

energy

intakes

of

breast-fed

infants

are

also

lower

than

those

of

formula-fed

in-fants,2#{176}even

at

6 and

9 months

when

other

foods

become

an

increasingly

large

proportion

of

total

in-take.

Furthermore,

at

these

ages

breast-fed

infants

typically

left

unconsumed

about

one

fourth

of

all

nonmilk

foods

offered

to

them,’9

implying

that

the

relatively

low

energy

intakes

observed

are

a function

of

infant

self-regulation

of

intake.29

There

was

no

evidence

that

the

nutritional

quality

of

complemen-tary

foods

offered

to the

breast-fed

cohort

was

lower

than

that

of foods

offered

to the

formula-fed

infants.

We

have

demonstrated

previously’9

that

the

slower

growth

rates

and

lower

energy

intakes

of

breast-fed

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TABLE

5. Length Increments (Centimeters per Month) of Breast-Fed and Formula-Fed Infants from 0 to 18 Months

Interval, mo Males Females

Breast-Fed Formula-Fed Breast-Fed Formula-Fed

No. Mean (SD) No. Mean (SD) No. Mean (SD) No. Mean (SD)

0-2 34 4.00 (0.98) 23 3.88 (0.77) 38 3.76 (1.02) 21 4.05 (1.00)

1-3 34 3.05 (0.62) 21 3.27 (0.49) 36 2.84 (0.50) 19 3.08 (0.60)

2-4 27 2.43 (0.44) 23 2.72 (0.62) 33 2.48 (0.53) 21 2.47 (0.58)

3-5 27 2.22 (0.56) 22 2.26 (0.52) 34 2.02 (0.49) 23 2.02 (0.59)

4-6 27 1.84 (0.51) 22 1.90 (0.40) 34 1.60 (0.52) 23 1.82 (0.55)

5-7 25 1.30 (0.63) 22 1.57 (0.49) 25 1.47 (0.48) 23 1.65 (0.64)

6-8 25 1.12 (0.46) 22 1.40 (0.49) 25 1.55 (0.47) 23 1.39 (0.47)

7-9 25 1.25 (0.49) 21 1.46 (0.36) 25 1.31 (0.43) 22 1.23 (0.53)

8-10 24 1.59 (0.53) 21 1.31 (0.54) 23 1.20 (0.50) 22 1.42 (0.48)

9-11 24 1.35 (0.39) 21 1.24 (0.56) 23 1.43 (0.39) 21 1.35 (0.49)

10-12 24 1.15 (0.45) 20 1.46 (0.47) 23 1.42 (0.45) 21 1.02 (0.46)

11-13 23 1.34 (0.47) 20 1.45 (0.80) 21 1.24 (0.57) 21 1.30 (0.52)

12-14 23 1.16 (0.41) 20 1.08 (0.61) 21 1.31 (0.46) 20 1.26 (0.57)

13-15 23 1.14 (0.40) 20 1.18 (0.40) 20 1.04 (0.46) 20 1.02 (0.65)

14-16 23 1.30(0.40) 20 1.19(0.47) 21 1.23(0.51) 18 1.20(0.59)

15-17 22 1.02 (0.31) 19 0.96 (0.43) 19 1.45 (0.36) 18 1.20 (0.62)

16-18 23 0.95 (0.48) 19 0.98 (0.53) 20 1.08 (0.45) 17 1.04 (0.43)

Repeated measures analysis of variance showed no significant differences between formula-fed males or females.

1040

GROWTH

OF

BREAST-FED

AND

FORMULA-FED

INFANTS

breast-fed and

infants

in our

population

are

not

associated

with

any

deleterious

consequences

in terms

of morbidity,

activ-ity

level,

or

behavioral

development.

Thus,

it seems

reasonable

to

conclude

that

it is normal

for

breast-fed

infants

to

gain

weight

less

rapidly

than

current

reference

data

suggest.

The

timing

of

differences

in

growth

velocity

is

worth

noting:

breast-fed

and

formula-fed

infants

had

similar

weight

gain

during

the

first

3 months,

but

breast-fed

infants

gained

less

rapidly

during

the

re-mainder

of the

first

year.

Weight

gain

during

the

first

12 months

in the

formula-fed

group

was

similar

to or

somewhat

higher

than

recently

published

reference

data.3#{176}Increments

in

length

were

generally

not

sig-nificantly

different

between

groups

(except

for

cu-mulative

length

gain

from

birth

to

1

2 months in

males).

These

findings

are

consistent

with

those

of

most

other

studies

in

affluent

populations.’7”5”6

Some

investigators

have

found

no

differences

in

growth

between

breast-fed

and

formula-fed

in-fants,8’

but

in

many

cases

the

studies

did

not

go

beyond

6 months,

or

the

definition

of

“breast-fed’

included

partially

breast-fed

infants

or infants

breast-fed

for

only

a few

months.

Because

of the

slower

growth

velocity

of breast-fed

infants,

when

their

growth

is

plotted

on

current

growth

charts

they

often

appear

to be “faltering’

after

the

first

2 to 3 months,6

even

if they

are

healthy

and

thriving.

As

a

consequence,

their

mothers

may

be

counseled

that

their

breast

milk

production

is

made-quate

and

that

complementary

formula

or

foods

should

be

added.

This

creates

a crisis

of

confidence

among

lactating

women

and

is a significant

barrier

to

programs

attempting

to

promote

exclusive

breast-feeding

during

the

first

6 months

of

life.

Incorrect

designation

of breast-fed

infants

as

showing

growth

faltering

may

be particularly

detrimental

to infants

in

developing

countries,

where

the

risks

associated

with

introducing

complementary

foods

under

unsanitary

conditions

are

high.3’

For

these

reasons,

it is apparent

that

new

growth

charts

based

on

breast-fed

infants

would

be

of value

in both

affluent

and

developing

countries,

as

others

have

pointed

out.3’6

In

the

meantime,

health

care

providers

counseling

parents

of young

infants

should

be

aware

of

the

differences

in

growth

patterns

of

breast-fed

and

formula-fed

infants.

ACKNOWLEDGMENTS

This work was supported by US Department of Agriculture grants 86 CRCR 1-1968 and 89-37200-4450 and by a gift from the Mead-Johnson Nutritional Group.

We are grateful for the expert assistance of Linda Stuart and Wendy Kristy, for the cooperation of study participants, for the help of our team of student assistants, and for comments on the

manuscript by Kenneth H. Brown.

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1982;2:275

3. Hitchcock NE, Gracey M, Gilmour Al, Owles EN. In: Falkner F, Kretch-ner N, Rossi E, eds. Nutrition and Growth in Infancy and Early Childhood.

Basel, Switzerland: Karger; 1986;19. Monographs in Pediatrics 4. Duncan B, Schaefer C, Sibley B, Fonseca NM. Reduced growth velocity

in exclusively breast-fed infants. AJDC. 1984;138:309-313

5. Salmenpera L, Perheentupa J. Siimes M. Exclusively breast-fed healthy infants grow slower than reference infants. Pediatr Res.

1985;19:307-312

6. Whitehead RG, Paul AA. Growth charts and the assessment of infant feeding practices in the Western world and in developing countries.

Early Hum Dev. 1984;9:187-207

7. Persson LA. Infant feeding and growth: a longitudinal study in three Swedish communities. Ann Hum Biol. 1985;12:42-52

8. Volz yR. Book LS, Churella HR. Growth and plasma amino acid

con-centrations in term infants fed either whey-predominant formula or

human milk. I Pediatr. 1983;102:27-31

9. Harrison G, Graver E, Vargas M, Churella H, Paule C. Growth and adiposity of term infants fed whey-predominant or casein-predominant

formulas or human milk. JPediatr Gastroenterol Nutr. 1987;6:739-747

10. K#{246}hlerL, Meeuwisse G, Mortensson W. Food intake and growth of

infants between six and twenty-six weeks of age on breast milk, cow’s

milk formula, or soy formula. Acta Paediatr Scand. 1984;73:40-48

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11. Jung E, Czajka-Narinf DM. Birthweight doubling and tripling times: an updated look at the effects of birthweight, sex, race and type of feeding.

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12. Saarinen UM, Siimes MA. Role of prolonged breast feeding in infant

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18. Dewey KG, Heinig MJ, Nommsen LA, L#{246}nnerdal B. Maternal vs infant factors related to breast milk intake and residual milk volume: the DARLING study. Pediatrics. 1991;87:829-837

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QUARTER-CENTURY-OLD

QUESTIONS-STILL

UNANSWERED

“To

what

extent

and

through

what

mediating

channels

do

social

and

economic

conditions

(as

reflected

by

parental

education,

income,

housing,

occupation)

affect

infant

and

pennatal

mortality?

How

much

of this

effect

is related

to the

type

and

quality

of care

received,

its availability

and

accessibility

and

the

motivation

to utilize

it? How

much

of the

effect

is an

outcome

of the

mother’s

earlier

growth

experience

in an

underprivileged

environment,

manifested

at conception

as a reduced

capacity

to bear

healthy

children?’

Shapiro 5, Moriyama IM, Yankauer A. Requirements for data on infant and perinatal mortality. Am

I

Public Health. 1967;57:1848-1861.

Submitted

by

Student

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(8)

1992;89;1035

Pediatrics

Lönnerdal

Kathryn G. Dewey, M. Jane Heinig, Laurie A. Nommsen, Janet M. Peerson and Bo

Study

Growth of Breast-Fed and Formula-Fed Infants From 0 to 18 Months: The DARLING

Services

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1992;89;1035

Pediatrics

Lönnerdal

Kathryn G. Dewey, M. Jane Heinig, Laurie A. Nommsen, Janet M. Peerson and Bo

Study

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References