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Original Article
Breastfeeding Frequency, Milk Volume, and Duration
in Mother–Infant Dyads with Persistent Nipple Pain
Holly L. McClellan, Anna R. Hepworth, Jacqueline C. Kent, Catherine P. Garbin,
Tracey M. Williams, Peter Edwin Hartmann, and Donna Tracy Geddes
Abstract
Background: Nipple pain and insufficient milk supply are major causes of early weaning. We have found that
persistent nipple pain was associated with strong infant sucking vacuums during breastfeeding. Several studies
indicate that nipple pain and abnormal infant sucking have the potential to reduce milk transfer. We aimed to
determine whether women with persistent nipple pain had low milk supply.
Subjects and Methods: The 24-hour milk production and feeding characteristics of mothers with persistent
nipple pain (n=21) were compared with those mothers without nipple pain (n=21). Milk productions were
measured by test-weighing the infant before and after every feed from each breast over a 24–26-hour period.
Comparisons were made using Student’s ttests and linear mixed models as appropriate.
Results: Lower milk productions were associated with longer meal durations for mothers with pain. There were
no significant differences in the average 24-hour milk production or any feeding characteristics between the
groups. However, four women with persistent nipple pain had milk production levels below 500 mL/day.
Conclusions: The majority of breastfeeding women experiencing persistent nipple pain were able to achieve
normal milk production levels. Feeding duration and frequency were similar to those of women not experi-
encing pain. However, longer meal durations in the pain group were associated with lower levels of milk
production. Further investigation is necessary to identify mothers most affected by maternal nipple pain.
Introduction
Although many cases of nipple pain can be resolved
with early treatment, pain and insufficient milk supply
are still common causes of early weaning.
1
Beyond the
experience-based advice of different positioning and at-
tachment techniques, few interventions exist for the treat-
ment of persistent nipple pain. In a recent study where
womenwithpersistentpainwereinstructedoncorrect
positioning and attachment, their infants were found to
apply stronger vacuums and transfer less milk during a
breastfeed compared with infants of mothers with no pain.
2
Furthermore, the time taken for the infant to feed from
one breast was similar for women experiencing pain and
those who were not.
Breastfeeding is a complex physiological process, and full
milk production is reliant upon adequate milk synthesis, se-
cretion, ejection, and removal from the breast.
3
During es-
tablished breastfeeding, milk synthesis rates are largely under
autocrine control, in that synthesis slows as breast fullness
increases.
4
Thus, ineffective milk removal will result in in-
complete breast drainage and down-regulation of milk syn-
thesis, which if prolonged may result in inadequate milk
production. Newton and Newton
5
demonstrated the poten-
tial for pain to interfere with breastfeeding; they found that
breastfeed volumes were significantly reduced by painful
distractions. This reduction was attributed to inhibition of the
milk ejection reflex, as the injection of oxytocin during the
distractions increased milk transfer to normal volumes.
5
It is
possible that the inhibition of milk ejection and strong sucking
vacuums may have contributed to the lower feed volumes
previously observed.
2
Because milk transfer may be lower in mothers with pain, it
is important to determine whether or not milk production is
consequently compromised. There is a large variation in milk
transfer between breastfeeds both within and between
mother–infant pairs, and the average volume of milk trans-
ferred during one breastfeed is inversely related to the num-
ber of breastfeeds over a 24-hour period.
6
Therefore, to
accurately estimate milk production it is imperative to mea-
sure milk transfer over a 24-hour period to take into account
the variations in feed volume and frequency.
This study aimed to investigate whether or not mothers
with persistent nipple pain had reduced 24-hour milk
School of Biomedical, Biomolecular, and Chemical Sciences, The University of Western Australia, Crawley, Western Australia, Australia.
BREASTFEEDING MEDICINE
Volume 0, Number 0, 2012
ªMary Ann Liebert, Inc.
DOI: 10.1089/bfm.2011.0117
1
production levels or altered feeding characteristics compared
with mothers without pain.
Subjects and Methods
Participants
All mothers were recruited from an ongoing study inves-
tigating infant sucking dynamics during breastfeeding. Upon
recruitment, mothers were invited to measure their milk
production levels at home. Nine of the 30 mothers in the
control group and 12 of the 30 mothers with persistent pain
agreed to measure milk production.
2
An additional 12 control
and nine pain mothers were recruited for this study.
The pain group consisted of mothers of healthy term in-
fants who were experiencing persistent nipple pain during
breastfeeding that had not resolved after assessment and
counseling by a lactation consultant (n=21). Mothers were
excluded from the study if a known clinical diagnosis for the
cause of their pain had been made, including either bacterial
or fungal nipple infection, nipple vasospasm, dermatitis, an-
kyloglossia, or torticollis. Women prescribed and taking ei-
ther steroids and/or antibiotics were excluded from the
study. The control group consisted of mothers breastfeeding
healthy term infants, who were content with their breast-
feeding relationship and not experiencing any pain during
feeding (n=21).
Ethics approval for the study was granted by the Human
Research Ethics Committee of The University of Western
Australia, and all participants supplied written, informed
consent to participate in the study.
Participant characteristics
Participant demographic and pain characteristics were
collected via a questionnaire. Variables recorded included
infant birth weight and gestational age, maternal age, preg-
nancy and postpartum complications, nipple pain, nipple
shield use, and frequency of feeding expressed breastmilk and
artificial formula. Maternal pain intensity was assessed im-
mediately after the monitored breastfeed of the breast with
the worst pain using the Visual Analogue Scale.
7
The duration
of pain was calculated by subtracting the reported day that
pain was initially experienced from the infant’s age.
Measurement of milk production
Each mother measured the volume of each feed from each
breast over a 24–26-hour period using the infant-test weight
method.
8
Mothers recorded the start and finish timesof the
feed and their infant’s weight before and after every breast-
feed for 24–26 hours on a Medela electronic BabyWeigh scale
(Medela AG, Baar, Switzerland). Feed volumes were calcu-
lated by subtracting the prefeed weight from the postfeed
weight. Expression volumes were calculated by weighing the
collection bottle before and after expressing.
Feeds were defined as a breastfeed from one breast. Feed
durations were calculated by subtracting the reported start
time from the reported end time. If a second feed started
within 30 minutes of the previous feed ending, then the two
feeds were classed as paired. If a third feed started within 30
minutes of the second feed ending, the three feeds were
classedasclustered.Amealwasdefinedeitherasanun-
paired breastfeed, two paired breastfeeds, or three clustered
feeds.
6
Meal durations were calculated by summing the
duration of all contributing feeds, excluding between-feed
intervals.
Measurement of sucking vacuum
Intra-oral vacuum was measured for an entire breastfeed
via a small Silastic(Dow Corning) tube attached to a pres-
sure transducer (Cobe Laboratories, Frenchs Forest, Aus-
tralia) taped alongside the nipple as previously described.
2,9
The pressure transducer was then connected via an inter-
connect cable (Cobe Laboratories) to the bridge amp (ADIn-
struments, Castle Hill, Australia) that was connected to a
Power Lab (ADInstruments), and data were analyzed using
the software package Chart version 5.0.2 (ADInstruments).
Average baseline and peak vacuums for the entire feed were
calculated for each infant.
Statistical analysis
Based on milk production data from Kent et al.,
6
it was
determined that this study had a power of 0.8 to detect a true
difference in milk productions of 130 g.
All analyses were performed using R version 2.9.0 for Mac
OS X.
10
The additional packages nlme
11
and lattice
12
were
used for linear mixed modeling and lattice plots, respectively.
Data are presented as mean –SD values except where the data
were not normally distributed, in which case the median (first
quartile, third quartile) is presented. Values of p<0.05 were
considered significant.
Total milk production was defined as the sum of the
amount of milk removed from both breasts, through breast-
feeding and breast expression, over the entire period, nor-
malized to 24 hours.
6
Breastfeeding variables defined for each
breast and normalized to a 24-hour period included milk
production, total feed duration, number of feeds, mean feed
duration, and mean feed volume.
Groups were compared on continuous variables using
Student’s ttest, with the Welch modification for unequal
variances used when Bartlett’s test of equality of variance
indicated heteroscedasticity. Distributions of milk production
levels in the two groups were compared with the two-sample
Kolmogorov–Smirnov test. Categorical variables were as-
sessed for group differences using Fisher’s exact test. Uni-
variate associations between measured variables and 24-hour
milk production have been assessed using either ttests or
linear regression as appropriate.
Relationships among 24-hour milk production, group, and
feeding characteristics were tested using regression models
with milk production as the response and measured variables
and group as predictors. All variables with a significant or
near significant ( p<0.1) univariate relationship to milk pro-
duction were included as predictors in the full regression
model, with the exception of confounding variables. Stepwise
selection was used, removing the least significant variable
until all included variables had a pvalue of <0.1.
Results
Demographics
No systematic differences were detected between the
two groups for any of the participant characteristics tested
(Table 1).
2 MCCLELLAN ET AL.
Pain characteristics
Women with persistent pain reported experiencing bilat-
eral pain for a median length of 66 (43, 89) days. The pain
intensities were lower for women who measured their 24-
hour milk production compared with those who did not:
measured, 22/100 (14, 44); not measured, 50/100 (36.5, 62.5)
(p=0.011).
Breastfeeding alternatives
Women in the pain group were significantly more likely to
feed expressed breastmilk ( p=0.043) (Table 1), although re-
ported daily pumping frequencies were not significantly dif-
ferent ( p=0.296). A low number of women expressed during
the monitored period (control, n=2; pain, n=4), and thus the
effect of expressing on milk production was not assessed.
Nipple shields
Nipple shield use was only reported in the pain group, with
five women regularly using a nipple shield ( p=0.048). When
low supply was defined as <500 g, there was a higher rate of
low supply in those using nipple shields ( p=0.028) within the
pain group.
Feeding characteristics
Feeding volume, frequency, and duration were similar for
the persistent pain and control groups, when either feeds or
meals were considered (Table 2) ( p>0.4 for all). In a 24-hour
period, the infants had an average of six meals of approxi-
mately 110 g, and feeding patterns for both groups are shown
in Figure 1.
Sucking vacuum
There was a trend for mothers in the control group to
measure milk production if their infant transferred less milk
during intra-oral vacuum measurement (measured,
55.1 –25.6 g, n=9; not measured, 78 –30.7 g, n=21 [p=0.085]).
Conversely, mothers in the pain group with higher milk
transfer during intra-oral vacuum measurement were more
likely to measure milk production (measured, 52.8 –37.5 g,
n=12; not measured, 34.0 –24.6 g, n=18 [p=0.021]). Infants in
the pain subgroup (n=21) of this study applied higher base-
line (pain, –91.5 –57.2 mm Hg; control, –38.4 –25.4 mm
Hg [p=0.003]) and peak (pain, –204.9 –61.8 mm Hg; control,
–151.7 –45.7 mm Hg [p=0.004]) vacuums during the moni-
tored feed compared with the control group (n=21). In the
women who measured 24-hour milk production, no
Table 1. Infant and Maternal Characteristics
Persistent
pain Control
p
value
Infant
Age (days) 75 (43, 96) 62 (43, 90) 0.547
Gestational
age (weeks)
39.0 (38, 39.4) 38.7 (38, 40.1) 0.466
Birth weight (kg) 3.25 (2.99, 3.85) 3.59 (3.1, 3.9) 0.375
Birth length (cm) 51.0 (48.5, 52) 51 (49, 53) 0.895
Apgar score 9 (9, 9) 9 (9, 9) 0.808
Time to first
breastfeed
(hours)
1 (0.25, 1.5) 0.6 (0.5, 2) 0.971
Sex female 10/21 11/21 1
Birth mode
vaginal
10/18 10/18 1
Expressed breastmilk
Daily 5/18 3/18 0.043
a
Weekly 2/18 3/18
Occasionally 6/18 0/18
Never 5/18 12/18
Formula
Daily 4/18 1/18 0.113
Weekly 0/18 3/18
Occasionally 0/18 0/18
Never 14/18 14/18
Pacifier
Mostly 2/18 4/18 0.443
Sometimes 10/18 10/18
Never 6/18 3/18
Maternal
Age (years) 32 (28.5, 34) 33 (29.5, 38) 0.143
Marital status
married/de facto
19/21 18/19 0.490
Parity primiparous 13/18 12/18 0.822
Education
High school 2/19 0/18 0.250
Trade certificate/
apprenticeship
1/19 0/18
College diploma 4/19 2/18
University degree 12/19 16/18
Cracked
nipples yes
13/19 5/19 0.063
Low supply yes 7/19 2/19 0.128
Engorgement yes 13/19 7/19 0.179
Mastitis yes 6/19 15/19 0.228
Data are presented as median (lower quartile, upper quartile) or
proportions.
a
Significantly different, p<0.05.
Table 2. Daily Feed Volume and Characteristics
for the Persistent Pain and Control Groups
Persistent
pain Control
p
value
Feeds
Number 12 (10, 12) 10 (10, 12) 0.694
Mean duration
(minutes)
18.7 (12.0, 24.7) 16 (13.0, 23.6) 0.441
Mean volume (g) 61 (48, 75) 61 (52, 77) 0.568
% feeds paired 100 (57.1, 100) 93.3 (54.5, 100) 0.874
Meals
Number 6 (6, 7) 6 (6, 7) 0.641
Mean duration
(minutes)
32.2 (22.9, 39.0) 31.3 (23.6, 40) 0.760
Mean amount (g) 108 (81, 138) 117 (94, 135) 0.654
Daily
Feed duration
(minutes)
214 (143, 262) 188 (151, 249) 0.935
Total milk
production (g)
738 (612, 905) 704 (615, 826) 0.957
Left breast (g) 363 (228, 413) 372 (281, 433) 0.518
Right breast (g) 350 (312, 518) 355 (269, 472) 0.614
Data are presented as median (lower quartile, upper quartile).
MILK PRODUCTION AND NIPPLE PAIN 3
difference in milk intake was seen for the monitored feed:
pain, 70 (38, 88) g; control, 68 (38, 80) g ( p=0.916).
Milk production
Although the range of 24-hour milk production measured
in the pain group (276–1,136 mL) was lower than that ob-
served for the control group (510–1,324 mL), there were no
significant differences in either the distribution ( p=0.603) or
the mean milk production ( p=0.957) between the pain and
control groups. Characteristics for the four women in the
pain group with 24-hour milk production levels below the
range seen in the control group ( <500 mL) are shown in
Table 3.
FIG. 1. The 24-hour milk intake patterns by breast for two control group (A and B) and two pain group (C and D) infants.
Feed volume transferred from the left (LB) and right breasts (RB) over a 24-hour period was measured using the infant test-
weigh method and plotted against the feed time and duration (rectangles). (A) and (C) demonstrate both paired and unpaired
feedings, whereas consistent paired feeds are shown for (B) and (D).
Table 3. Milk Production and Feeding Characteristics of Four Mothers with Persistent
Pain and Low Milk Production
Mother
1234
Milk production (g) 275 434 437 486
Feeds/day 10 16 11 7
Mean feed amount (g) 16.4 27.2 59.4 69.5
Mean feed duration (minutes) 29.1 25.6 23.6 24.5
Meals/day 5 8 7 5
Mean meal amount (g) 36 59.4 59.7 99.7
Mean meal duration (minutes) 77.3 56.9 38.1 38
Vacuum (mm Hg)
Baseline -251.0 -57.3 -49.8 -93.4
Peak -318.1 -218.4 -161.0 -142.1
Expression frequency 5/breast/day <1/day 3/breast/day <1/day
Formula Yes No Yes Yes
Use of nipple shield Yes Yes Yes No
4 MCCLELLAN ET AL.
Significant univariate predictors of higher 24-hour milk
productions were higher average feed ( p<0.001) and meal
volumes ( p<0.001) and shorter average meal duration
(p=0.008). Trends to higher milk production were demon-
strated with increased infant age ( p=0.066), vaginal delivery
(p=0.078), and shorter average feed durations ( p=0.054).
There was no association between 24-hour milk production
and baseline ( p=0.589), peak vacuum ( p=0.443), or infant sex
(p=0.449). No significant univariate associations were de-
tected between any of the remaining variables and 24-hour
milk production.
There were different relationships seen between meal
duration and 24-hour milk production for the two groups
(Fig. 2). Although there was no relationship between meal
duration and milk production for the control group
(p=0.801), in the pain group an increase of 1 minute in meal
duration was associated with a decrease of around 9 mL in
milk production ( p=0.017). Thus, in the pain group, short
meal durations had higher milk productions than those with
similar meal durations in the control group, those with meal
durations of approximately 33 minutes had similar produc-
tions, and those with long meal durations had lower milk
productions than the control group.
When all measured variables were considered, the best
linear regression model took into account meal duration and
volume and mode of delivery, with shorter meal durations
(p=0.011), greater meal volumes ( p<0.001), and vaginal de-
livery ( p=0.048) being significant predictors of higher 24-
hour milk production.
Discussion
This study has shown that despite experiencing pain dur-
ing breastfeeding, mothers with persistent nipple pain are
able to achieve a full milk production. Furthermore, these
women fed with similar duration and frequency as women
not experiencing pain. The feed characteristics and milk pro-
ductions of these mothers are similar to those of other cohorts
of breastfeeding women not experiencing pain.
6,13
The similar
feeding characteristics suggest that pain does not result in
lower 24-hour milk production as a consequence of fewer or
shorter feeds and does not require more frequent or longer
feeds. It is possible that the professional assistance received by
mothers with pain may have contributed to this outcome.
Also, the mothers recruited for this study had a high socio-
demographic status, which is associated with longer length of
breastfeeding.
14–17
Thus, these women were likely to be
highly motivated to breastfeed despite experiencing pain.
As the volume of milk transferred during a 24-hour period
was similar for both groups, it is unlikely that the milk ejection
reflex was adversely affected by the pain experienced during
breastfeeding. Presumably, if the milk ejection reflex were
impaired, milk transfer rates during feeding would have been
lower for these women. In the study of Newton and Newton,
5
painful distractions resulted in decreased milk transfer for one
feed, and the volume of milk received by the infant could be
increased by the injection of oxytocin, the hormone that
stimulates milk ejection. It is interesting that distractions that
reduce milk transfer have been found to have less impact over
time, as the mother becomes conditioned to the stimuli.
5
Therefore, it is conceivable that the women in this study may
have become conditioned to experiencing pain over time.
Previously, we found that feed volumes were reduced in
infants with strong sucking and mothers with persistent
pain.
2
In this study, neither the mean baseline nor peak vac-
uum levels were related to milk production. Similarly, no
relationships were detected between feed/meal durations
and baseline/peak vacuums. This suggests that although
strong sucking vacuums are applied neither milk synthesis
nor removal rates are affected.
FIG. 2. Relationship between 24-hour milk
production and average meal duration for the
pain and control groups. Regression lines for
the relationship between meal duration and 24-
hour milk production are shown for each group
(pain =triangles, control =circles). The trend for
infants in the pain group represents higher
volumes at low meal durations and lower vol-
umes at higher meal durations. The regression
lines of the two groups intersect at approxima-
tely 33 minutes, indicating average meal dura-
tions longer than 33 minutes were associated
with lower 24-hour milk production levels in
the pain group.
MILK PRODUCTION AND NIPPLE PAIN 5
In the final regression model to predict 24-hour milk pro-
duction volume, higher mean meal volume, shorter mean
meal duration, and vaginal delivery were significantly asso-
ciated with higher milk production. Thus it may be worthy to
investigate the affect of mode of birth on established milk
production levels in a larger cohort. Mode of birth has been
recently shown to be associated with delayed onset of lacta-
tion
18
and reduced breastmilk transfer from Days 2 to 5
postpartum,
19
compared with vaginal deliveries. Thus ce-
sarean section may be a barrier to breastfeeding success and
worthy of further consideration.
Clinically, the only predictor of lower milk production was
meal durations lasting longer than 33 minutes in the women
with persistent nipple pain, and longer meal durations were
not associated with lower milk productions in the control
group. Reasons for long meal durations could be due to either
maternal opinion of minimum feeding durations or that the
infant may not appear to be settled and satiated at the end of
the feed. Thus, it may be useful to monitor milk transfer in
women who report long meal durations. It is interesting that
in this study we did not find a relationship between infant
sex and milk production, which differs from the previous
findings of significantly higher milk productions ( p=0.036)
between mothers of boys (831 –187 g) and those of girls
(755 –151 g).
6
Caution is required when applying these results to all
mothers with persistent pain, as recruited mothers who
measured their milk production differed from those who did
not in two respects. First, those women who measured their
milk production reported lower pain intensities than those
who did not. The task may have been too onerous for those
experiencing higher-intensity pain. Breastfeeding character-
istics, such as feeding duration or expression frequency, may
be different in women with high pain intensity as interference
levels are likely to be higher. Also, it is unknown whether
higher pain intensities affect oxytocin release, and subse-
quently milk transfer volume. Second, unlike our previous
study of infant sucking vacuum,
2
milk transfers for the
monitored feed were not different between the two groups
(p=0.916). Women in the control group tended to measure
their milk production if milk transfer during the monitored
feed was lower, possibly for reassurance, whereas women in
the pain group with higher milk transfer during the moni-
tored feed were more likely to measure milk production.
These tendencies may explain the more homogeneous spread
of monitored milk intakes between groups in this study.
Therefore, further investigation of a larger cohort of women
with pain, especially those with high-intensity pain and low
feed transfer, is necessary to determine which breastfeeding
dyads may experience low milk production.
In this study, breastfeeding mothers with pain were more
likely to use nipple shields and feed expressed breastmilk
than breastfeeding mothers without pain as a means of re-
ducing the level of their pain. Three of the five women expe-
riencing pain and using nipple shields had low milk
production ( <500 mL). Nipple shields are not generally re-
commended as an intervention for nipple pain unless moni-
tored by a knowledgeable health professional. Studies of the
effect of nipple shields on milk transfer are conflicting. Early
studies have associated nipple shields with reduced milk
transfer,
20,21
whereas more recent research in preterm and
term infants suggests that ultrathin nipple shields do not af-
fect milk transfer.
22–24
Because it is not known whether the
low milk production measured in mothers who were using
nipple shields in this study was due to the shield itself or other
factors that might potentially influence supply such as pain or
low prolactin levels, monitoring of mothers using shields is
strongly supported. Because of the small numbers of mothers
using shields in this study, further research is required into the
effect of nipple shields on milk transfer in term infants whose
mothers experience pain.
Conclusions
It is possible that with professional support, breastfeeding
women experiencing low-intensity persistent nipple pain can
achieve a full milk production despite their infants applying
strong vacuums. Those women who had difficulty reaching
full milk production were not breastfeeding less frequently and
were more likely to have long breastfeeding meal durations.
Further research is required to determine if mothers with high-
intensity nipple pain have compromised milk production.
Acknowledgments
Financial support in the form of a Ph.D. scholarship and
unrestricted research grant was received from Medela AG,
Switzerland.
Disclosure Statement
No competing financial interests exist.
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Address correspondence to:
Donna T. Geddes, D.M.U., PostGrad Dip. (Sci.), Ph.D.
School of Biomedical, Biomolecular, and Chemical Sciences
The University of Western Australia
M310, 35 Stirling Highway
Crawley, WA 6009, Australia
E-mail: donna.geddes@uwa.edu.au
MILK PRODUCTION AND NIPPLE PAIN 7
