Effect of Frequent Breast-Feeding on Early Milk Production and Infant Weight Gain

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Effect

of Frequent

Breast-Feeding

on Early

Milk Production

and Infant

Weight

Gain

Manoel

De Carvalho,

MD, Steven

Robertson,

PhD,

Arnold

Friedman,

MD, and

Marshall

Klaus,

MD

From the Department of Pediatrics, The Mount Sinai Medical Center and Rainbow Babies and Chlldrens Hospital, Case Western Reserve University, Cleveland

ABSTRACT.

To investigate the effects of frequency and

duration of breast-feeding on infants’ milk intake and

weight gain, two groups of mother-infant pairs were

studied during the first month after delivery. Mothers in the control group (n

=

24) nursed their infants on a 3- to 4-hour schedule. Those in the experimental group (n =

20) were encouraged to nurse frequently. During the first

14 postpartum days, all mothers recorded the length and time of each breast-feeding. On the 15th and on the 35th postpartum day, milk intake per feeding for 24 hours and

infant weight gain from birth were measured. During the

first 2 weeks after delivery, mothers in the experimental group nursed more frequently (9.9 v 7.3 feedings per 24 hours; P < .0001). On day 15, their infants took more milk (725 v 502 mL/24 h; P < .0002), and had gained

more weight from birth (561 v 347 g; P < .02). On day 35, although mothers in the experimental group were still

nursing more frequently (9.8 v 6.8 feedings per 24 hours; P < .01), milk intake and weight gain from birth were not significantly different. Pediatrics 1983;72:307-311; breast-feeding, breast milk, feeding frequency, milk intake.

Insufficient milk production continues to be the major cause of early lactation failure even though

the incidence of breast-feeding has increased in

recent years.17 In Western societies, more frequent

demand is often interpreted as an indication of

inadequate milk supply.5 Although demand feeding

has been recommended for newborn infants for

many years, nursing mothers are often advised to

limit the duration and frequency of feedings to

prevent nipple soreness in early lactation. However,

scheduled and widely spaced feeding regimens

Received for publication Oct 18, 1982; accepted Dec 14, 1982.

Read, in part, before the Annual Meeting of the Society for

Pediatric Research, Washington, DC, May 11-13, 1982.

Reprint requests to (M.D.) Rainbow Babies and Childrens

Hos-pital, 2101 Adelbert R.cI, Cleveland, OH 44106.

should be reevaluated as recent data show that

frequent and unlimited feedings in early lactation

are associated with lower serum bilirubin levels,

more successful lactation, and no increase in the

incidence of nipple soreness.8’9 The purpose of this study was to investigate the effects of frequent and

unrestricted breast-feeding on infants’ milk intake

and growth during the first month after birth.

MATERIALS

AND METHODS

Mothers at The Mount Sinai Medical Center of

Cleveland who had an uncomplicated term

gesta-tion, normal labor and delivery, and who planned

to breast-feed were asked to participate in the

study. A written consent form was completed after

an explanation of the research design was made by

one of the investigators. Mothers delivering during

the months ofJuly and August (control group), who

agreed to participate in the study, were told shortly

after delivery to feed their infants according to the hospital routine (3- to 4-hour schedule). Mothers

delivering during the months of September and

October (experimental group) were encouraged to

nurse on true demand. They were instructed to feed

their infants whenever they seemed to be hungry

(fussiness, sucking of fingers, mouthing

move-ments). Otherwise, the instructions for both groups

of mothers were similar and took the same amount of time. This design was selected to limit conflicting

information being given to nursing mothers in the

postpartum ward. All mothers in our study attended

one breast-feeding class during their hospital stay,

and they were taught basic breast care techniques.

Maternal age and parity were similar in both groups

(Table 1). Breast-feeding began within six hours of delivery.

During the first 14 days after delivery, all mothers recorded the length and time of each breast-feeding.

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(mean ± SD) and on day 35 ± 3, by weighing the

infants before and after each breast-feeding for a

period of 24 hours. Mothers used an electronic scale with accuracy within 2 g (Toledo/8130 periodically

calibrated with a known weight), coupled to a digital display. They were instructed not to change their

infant’s diaper between weighings in the same

as-sessment. To minimize error, they recorded their

infant’s weight three times before and three times

after each feeding. The mean weight before and

after feeding was then calculated for each time they

fed their infant. Milk volume was assessed

assum-ing 1 g/mL. During the test weighing periods they

also recorded the duration of each feeding episode. Patients were not included in the data analysis

if they did not have a complete recording of the

time and duration of feedings during the study

period, or if they were unable to perform the

weigh-ing for a complete 24 hours. Mothers who withdrew

from the study did so because “there was too much

to record.” Mothers were also eliminated from the

study if they were supplementing with bottle

feed-ings. The reason for supplementation was not

as-sessed.

Results are expressed as the mean ±1 SD (range). Student’s t test and Pearson correlations were used for the statistical analysis of the data. The

magni-tudes of correlations are reported only when P < .05.

Control

Group

Initially, 47 patients were enrolled. By the 15th day, 23 patients were eliminated (13 patients were

supplementing with formula, four had discontinued

the study, two could not be contacted, and four did

not have a complete record of the frequency and

duration of feedings during the first 14 days after

delivery).

Thus,

24 mother-infant pairs (11 mothers

were primiparous) constitute the subjects for the

first assessment. The infants (13 boys and 1 1 girls)

were all vaginally delivered and had birth weights

of 3,045 ± 477 g (2,520 to 4,300); all had one-minute

Apgar scores 7 (8.8 ± 0.6); and none had postnatal

complications. By day 35, another eight patients

were eliminated (two discontinued the study, four

were supplementing with formula, and two could

not be contacted). The birth weight and Apgar

scores of these eight infants did not differ from the

remaining 16 (ten boys and six girls) who were

studied on the second assessment. Data for patients

eliminated from the study are shown in Table 2.

Experimental

Group

Of the 28 patients initially enrolled, eight were

eliminated by day 15 (five were supplementing with formula and three had incomplete data recording).

Thus, 20 mother-infant pairs (ten mothers were

primiparous) were studied on day 15. The infants

(11 boys and nine girls) were all vaginally delivered

and had birth weight of 3,523 ± 326 g (3,120 to

4,070); all had one-minute Apgar scores 8 (9.0 ±

0.7); and none had postnatal complications. For the

second assessment, another eight patients were

eliminated (three were supplementing with

for-mula, two had incomplete data recording, two could

not be contacted, and one discontinued the study)

(Table 2). The birth weight and Apgar scores of

these eight infants did not differ from the remaining

12 (five boys and seven girls) who were studied on

the second assessment.

RESULTS

Days I to 14

The daily frequency and duration of feedings in

the first 2 weeks post partum are shown in Fig 1.

Mothers in the experimental group nursed an

av-erage of 9.9 ± 1.9 times per 24 hours, whereas those

in the control group nursed 7.3 ± 1.4 times per 24

hours (Table 3). Although the frequency of feedings

was significantly different in the two groups (P <

.0001),

the mean total duration of feeding (minutes

per 24 hours) was similar (134 v 138 min/24 h)

(Table 3).

Day 15

The mean feeding frequency on the 15th

post-partum day was 9.9 ± 2.5 feeds per 24 hours in the

experimental group and 7.5 ± 1.7 feeds per 24 hours

TABLE 1.

Demographic Characteristics of Mothers in Study

Enrolled Day 15 Day 35

Experimental Control Experimental Control Experimental Control

Group Group Group Group Group Group

Total 28 47 20 24 12 16

No. primiparous 13 20 10 11 6 7

Maternal age (yr)* 26.7 ± 4.7

(19-38)

26.4 ± 5.8 (18-35)

27.0 ± 2.6 (22-38)

28.7 ± 3.8 (18-35)

27.0 ± 2.6 (23-32)

28.7 ± 3.8 (23-35)

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LJ4#{248}LJJJJ4LtLLLJ

14 12

10

8 6 4

210

170

130

90 50

,,irTItTTTT1U

r

I

T

I

(0 0 I CsJ

z

35 Fig 1.

Daily frequency and duration of breast-feedings in control (dashed line) and

experimental groups (solid line) during first month after birth (mean ± SD).

DAYS AFTER

BIRTH

TABLE 2.

Patients Eliminated from Study*

D ay 15 Da y 35 Total

Experimental Control Group Group Experimental Control Group Group Experimental Group Control Group Formula supplement Incomplete recording Withdrew

Change of address

5 (17.9) 3 (10.7) ... ... 13 (27.6) 4 (8.5) 4 (8.5) 2 (4.3) 3 (10.7) 2 (7.1) 1 (3.6) 2 (7.1) 4 (8.5) ... 2 (4.3) 2 (4.3) 8 (28.6) 5 (17.9) 1 (3.6) 2 (7.1) 17 (36.0) 4 (8.5) 6 (12.8) 4 (8.6)

Total 8 (28.6) 23 (48.9) 8 (28.6) 8 (17.0) 16 (57.1) 31 (66.0)

* Values are number of subjects; percent is shown in parentheses.

(0

a

z

0 w w LI-O

>-O

ox

z

w LI (0

a

z

0 w w LI 0

z

0 I-0

in the control group (P <

.001).

Infants in the

experimental group consumed more milk on day 15

(725 V 502 mL/24 h; P < .0002) and had gained

significantly more weight from birth (561 v 347 g;

P < .02) than those in the control group (Table 3).

The mean duration of feedings was 142 ± 39

mm-utes V 153 ± 49 min/24 h (P > .10). In both groups, milk intake was not significantly correlated with

the duration of feedings on day 15 or the mean

duration for days 1 through 14.

Day 35

The mean frequency and duration of feedings on

the 35th postpartum day are shown in Fig 1 and

Table 4. The mean frequency of feedings for infants

in the experimental group was 9.8 ± 2.4 feedings

per 24 hours and for those in the control group was

6.8 ± 1.2 feedings per 24 hours (P < .01). The mean duration of feedings was not significantly different between the groups (177 v 152 min/24 h, P > .10).

There was a significant correlation between the

mean frequency of feeding during the first 14

post-partum days and on the 35th day in the control

group (r

=

.74, P < .001), but not in the

experimen-tal group. There was no correlation between feeding

frequency on days 15 and 35. In both groups the

mean duration of feedings (minutes per 24 hours)

from days 1 to 14 and on day 15 were significantly

correlated with the duration of feedings on day 35

(r

=

.58 and r

=

.68, respectively, for the control

group; r

=

.57 and r

=

.62, respectively, for the

experimental group; P <

.05).

The average daily milk intake by infants in the

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r .52 P< .05

r=.69

P<.02

7

Day Day Day Day

15 35 15 35

CONTROL EXPERIMENTAL

TABLE 3.

Comparison of Experimental and Control Groups on Days 1 to 15*

Group Days 1 to 14 Day 15

Frequency of Duration of Milk Intake Weight Gain from

Feedings/24 h Feedings (mL/24 h) Birth (g)

(min/24 h)

Experimental 9.9 ± 1.9 134 ± 48 725 ± 171 561 ± 286t

(6.8-13.6) (66-223) (368-1,045) (216-847)

Control 7.3 ± 1.4 138 ± 39 502 ± 185 347 ± 331

(5.4-10.4) (74-225) (294-902) (-555-858)

* Values are means ± SD; range is shown in parentheses.

tPz.02. tP< .001.

TABLE 4.

Comparison of Experimental and Control Groups on Day 35*

Group Frequency of Duration of Milk Intake Weight Gain from

Feedings/24 h Feedings (mL/24 h) Birth (g)

(min/24 h)

Experimental 9.8 ± 2.4t 177 ± 73 841 ± 285 1,350 ± 418

(6-14) (79-345) (411-1,315) (676-2,148)

Control 6.8 ± 1.2 152 ± 53 681 ± 179 1,246 ± 356

(5-9) (58-232) (320-1,021) (696-2,005)

* Values are means ± SD; range is shown in parentheses.

tP<.01.

1300

- 1150

2

1000

850

:

700

550

400

> 250

Fig 2.

Milk intake on postpartum days 15 and 35 in

control and experimental groups. (Only values for pa-tients with data for both assessments are shown.)

was not significantly different from that in the

control group (841 v 681 mL; P

=

.08). Milk intake

was not significantly correlated with the frequency

or duration of feedings. For both groups, milk

in-take on day 35 was higher than on day 15 (Fig 2).

Milk intake increased 133 ± 206 mL/24 h in the

experimental group (P < .05) and 182 ± 172 mL/

24 h in the control group (P < .001) (Fig 2). These increases are not significantly different. Milk in-take on the 15th postpartum day was significantly

correlated with milk intake on the 35th day in both

groups (Fig 2). By day 35, weight gain from birth

was not significantly different between the groups

(Table 4).

DISCUSSION

This study demonstrates that frequent and

un-restricted breast-feeding increases early milk pro-duction and infant weight gain. These findings are of practical relevance as insufficient milk produc-tion is the major cause of early lactation failure.’T Success in the early period of lactation is strongly

influenced by maternal anxiety. Emotional stress

can jeopardize the success of breast-feeding by in-hibiting the oxytocin-induced letdown reflex.’#{176} A slow infant weight gain in this period increases the

mother’s uncertainty about her milk supply.”

Al-though a rapid weight gain in later infancy is not necessarily desirable, in early lactation a fast infant weight gain gives the mother reassurance and

con-fidence in the adequacy of her milk supply.

Al-though recent data suggest that early initiation and

frequent breast-feeding are associated with

in-creased success of lactation, a longitudinal follow-up was not done in our study.12

The similarity of the two groups for the total

duration of nursing in spite of different frequency of feedings, and significant correlations between the duration of nursing in the first 14 days and on

the 35th postpartum day in both groups, confirms our previous findings and suggests that for

individ-ual infants the length of nursing is fairly constant regardless of the frequency of feeding.13

In a previous correlational study,13 no significant relationship was found between breast-feeding

fre-quency and milk intake. However, in that study,

milk intake was measured only on the 34th day

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relationship between feeding frequency and milk intake when both are measured in the first 2 weeks

of lactation. Neither study found a significant cor-relation between feeding frequency and breast milk consumption at 1 month. Rattigan et al,’4 studying 27 nursing mothers, found a significant correlation

between feeding frequency and milk production. However, in that study patients were divided into small groups (n

=

4 or 5) according to their stage

of lactation (1 to 15 months), mothers who were

partially breast-feeding were included, and the

cor-relation between feeding frequency and milk

pro-duction pooled the data from all time periods.

On the 15th day after delivery, mothers in the

experimental group were producing more milk than

those in the control group. However, it is interesting

to note that although the frequency of feeding

re-mained significantly different on the 35th

postpar-tum day (second assessment), milk intake and

weight gain from birth were not significantly

dif-ferent between the two groups. This suggests that

frequent feeding in early lactation stimulated a

faster increase in milk output and that this incre-ment was slower thereafter despite the continuation

of the frequency of breast stimulation. Recent data

in animals suggest that suckling stimulates the

development of receptors to prolactin in the

mam-mary gland and that the number of receptors per

cell increases in early lactation and remains

con-stant thereafter.’57 In our study, it is possible that frequent feedings in the experimental group

stim-ulated an early increase in prolactin receptors in

the breast, resulting in greater milk output on day

15.

Detailed knowledge of circulating levels of ma-ternal prolactin in both groups would have provided additional information on the relationship between

feeding frequency and milk production over time. In conclusion, our report presents evidence that

milk production and infant weight gain can be

significantly increased in early lactation by a sim-ple, low-cost intervention. This finding is of clinical importance for breast-feeding mothers in Western societies, but may have even more far-reaching

implications on the health and survival of infants in developing nations.

ACKNOWLEDGMENT

This work was supported, in part, by the Thrasher Research Fund and the William T. Grant Foundation.

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16. Sernia C, Tyndale-Biscoe CH: Prolactin receptors in the mammary gland, corpus luteus and other tissues of the

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1983;72;307

Pediatrics

Manoel De Carvalho, Steven Robertson, Arnold Friedman and Marshall Klaus

Effect of Frequent Breast-Feeding on Early Milk Production and Infant Weight Gain

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