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 andduration 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.
PEDIATRICS (ISSN 0031 4005). Copyright © 1983 by the American Academy of Pediatrics.
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.
(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 motherswere 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 (minutesper 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 StudyEnrolled 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)
LJ4#{248}LJJJJ4LtLLLJ
14 1210
8 6 4210
170
130
90 50,,irTItTTTT1U
r
I
T
I
I
(0 0 I CsJz
35
Fig 1.
Daily frequency and duration of breast-feedings in control (dashed line) andexperimental 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 (0a
z
0 w w LI 0z
0 I-0in the control group (P <
.001).
Infants in theexperimental 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 theexperimen-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 controlgroup; r
=
.57 and r=
.62, respectively, for theexperimental group; P <
.05).
The average daily milk intake by infants in the
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
1000850
:
700550
400
> 250
Fig 2.
Milk intake on postpartum days 15 and 35 incontrol 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 intakewas 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
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 stageof 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 betweenfeeding 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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