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54 un J C/in Niar 1993:58:54-60. Printed in USA. 1993 American Society for Clinical Nutrition
Delayed lactogenesis in women with insulin-dependent
diabetes mellitus14
Su:anne H Neuhauer. .4 nn lvi Ferris. Christina G Chase, Joanne Fane/li, Co/leen A Thompson.
Carol J Lammi-Keefe. Richard M Oark. Robert G Jensen. Robert B Bendel. and Karen W Green
ABSTRACT Breast milk lactose. total nitrogen. conductiv-
ity. osmolality. and intake by infants of33 women with insulin-
dependent diabetes mellitus (IDDM). 33 control women without
diabetes. and I 1 reference women were determined in a 3-mo
study oflactation. Milk ofwomen with IDDM had significantly
lower lactose and higher total nitrogen (2-3 d postpartum). and
their infants had significantly less milk intake (7-14 d postpar-
tum) than did control or reference women. Total nitrogen was
negatively correlated with milk lactose for women with IDDM
at all times and for control women through day 14 postpartum.
The data indicate delayed lactogenesis for women with IDDM.
which was more likely to occur with poor metabolic control.
Differences in milk composition ofwomen with IDDM do not
preclude them from breast-feeding their infants. .4,ii J Clin
Nutr 1993:58:54-60.
KEY WORDS Lactation. initiation of lactation. breast-
feeding. human milk. milk composition. insulin-dependent di-
ahetes mellitus, metabolic control. breast milk intake. test
weighing
Introduction
The ability ofsome women with insulin-dependent diabetes
mellitus (IDDM) to breast-feed has been documented ( 1. 2) as
has preliminary information on the unique aspects oftheir din-
ical management (2). Although women with IDDM choose to
breast-feed as often as do women without diabetes (2). clinical
research concerning lactation in women with IDDM is limited.
Milk lactose is thought to be a marker for lactogenesis (3. 4).
Lactose increases while protein. sodium. and chloride decrease
(5. 6): these changes precede the increase in milk volume secre-
tion (7). Arthur et al (4) found that the onset ofcopious milk
secretion at 24-48 h postpartum, was delayed significantly in
women with IDDM: however, breast milk lactose reached a pla-
teau by day 4 postpartum in women with and without IDDM.
Bitman et al (8) studied one woman with IDDM and determined
that milk volume at 3 d postpartum was lower than that of a
normal reference group but normalized by day 5 postpartum.
Euglycemia may influence milk composition and ultimately
affect lactation outcome. Hyperglycemia in alloxan-induced
diabetic rats or goats resulted in decreased milk lactose and
protein (9. 10). Milk yields were also decreased. Insulin ad-
ministration reversed these effects: however, permanent loss
of mammary gland function occurred when insulin was with-
held ( I 1 ). At 90 d postpartum. Butte et al ( 12) studied breast
milk ofwomen with IDDM who had elevated hemoglobin (Hb)
A, concentrations. Breast milk lactose and protein were the
same as that ofa reference population but glucose and sodium
were significantly higher. Hypoglycemia may also occur in
women with IDDM: it has been found in the early postpartum
period and after breast-feeding (2. 13). Hypoglycemia in ani-
mals increased epinephrine. which in turn decreased blood flow
to the mammary gland ( I 4. 1 5). Decreased lactate with in-
creased ketone production was accompanied by decreased
mammary gland lipogenesis (16). Ultimately breast milk corn-
position may be affected.
Because breast milk composition ofwomen with IDDM and
intake by their infants have not been evaluated longitudinally,
the present study investigated lactation in women with IDDM
by determining for 3 mo breast milk composition of lactose,
total nitrogen. conductivity. osmolality, and intake by infants
of women with IDDM. Electrical conductivity was used to
measure anion and cation changes in milk that occur with the
initiation oflactation ( I 7). Ifmilk ofwomen with IDDM differs
in lactose and electrolytes. then milk osmolality might also be
affected. Morriss ( 18) has reviewed the effects of hyperosmolar
milk on infant conditions. Because women with IDDM must
depend on exogenous insulin to maintain euglycernia and
fine-tuned control is difficult to achieve, we also wished to
study the effect of metabolic control in women with IDDM
on the above markers of lactogenesis and intake by their
infants.
I From the Department of Nutritional Sciences and the Center for
Environmental Health. Department of Animal Science, University of
Connecticut. Storrs. and the Division of Maternal-Fetal Medicine. Uni-
versity ofMassachusetts Medical School. MCCM-Memorial. Worcester.
MA.
2 Scientific Contribution Number 1385. Storrs Agricultural Experiment
Station. University ofConnecticut. Storrs.
3 Supported in part by funds made available through NICHHD ROl-
HD20208. the Hatch Act. the University of Connecticut Research
Foundation. and the Pediatric Nutrition Dietetic Practice Group of the
American Dietetic Association.
4 Address reprint requests to AM Ferris. Department of Nutritional
Sciences. U- I 7, 3624 Horsebarn Road Extension. University of
Connecticut. Storrs. CT 06269-40 17.
Received February 25. 1992.
Accepted for publication January 19. 1993.
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DELAYED LACTOGENESIS AND DIABETES
55
Methods
Subjects
The study population consisted of 33 lactating women with
IDDM, 33 lactating women without IDDM (control subjects),
and 1 1 healthy reference women as outlined previously (19).
The study had human subjects approval by all hospitals used
for recruiting (19) and by the University ofConnecticut. Women
were recruited through private obstetricians’ offices and high-
risk prenatal screening clinics at three medical centers. Data on
breast milk intake were obtained from a subgroup of mothers
who did not differ from the study population with respect to
subject characteristics. This subgroup was determined solely by
the willingness of the mother to participate. This subgroup in-
eluded 18 lactating women (control) pair-matched to 18 women
with IDDM. 10 reference women, and their infants. Matching
characteristics of the subgroup were as follows: gestational age.
< 37 (n = 1) and 37 wk (n = 17): delivery method. vaginal
(n = 7) and cesarean section (n = 1 1 ): infant sex, males (n = 12)
and females (n = 6): prior lactation, yes (n = 9) and no (n = 9).
Five ofthe 10 reference women had prior lactation experience.
and the sex of their infants was 5 males and 5 females.
(‘ollection procedures
Subjects were visited at days 2 and 3 postpartum in the hospital
and at days 7 ± 1, 14 ± 2. and 42 and 84 ± 4 postpartum in
the hospital or at home ( 19). Blood samples were drawn 80 mm
after breakfast. HbA1 samples. drawn at 3 and 42 d postpartum,
were transported immediately on wet ice packs to the hospital
laboratory or sent by overnight mail in styrofoam containers.
HbA samples were sent to Smith Kline Bio-Science Labora-
tories (63.0%) (Waltham, MA) or Nichols Institute (37.0%) (San
Juan Capistrano. CA) for analysis. An HPLC analyzer and Hb
autodiluter semiautomated system were used. There were no
significant differences in average HbA1 concentrations with re-
spect to the laboratory where analyzed: therefore, the data were
combined for subsequent analyses. Capillary blood samples were
analyzed for glucose at each visit. Either an Accu-Chek bG
(Boehringer-Mannheim, Indianapolis) or a Glucoscan 2000
(Lifescan, Mountain View, CA) reflectance meter was used.
Both instruments were reported to accurately reflect venous
glucose (20).
All milk samples were collected by trained researchers using
an Egnell electric pump (Egnell Inc. Cary, IL). Milk expression
was done immediately after blood glucose was determined. To
ensure a representative milk sample, mothers were asked to
breast-feed their infants before breakfast, thus ensuring a I-h
interval between breast-feeding and sampling. The breast pump
was held to the breast until milk no longer came out in an even
intermittent stream, 8 mm/breast. At days 2 and 3 postpartum
the mothers’ breasts were pumped for a maximum of 5 mm if
no sample was available. The procedure always began on the
right breast and was repeated for the left breast. All analyses
were done on samples from both left and right breasts. Samples
for nutritional analyses were immediately frozen at the collection
site on dry ice and transferred to a freezer (-70 #{176}C)until ana-
lyzed. When there was adequate milk, fresh milk for conductivity
and osmolality was sampled, transported to the laboratory on a
wet ice pack, and analyzed within 4 h.
Breast milk intakes were determined at 7, 14, 42, and 84 d
postpartum by test weighing the infant before and after each
feeding for 24 h plus one more feeding. A model 3862MP8
(Sartorius, Gottingen, Germany) integrating electronic balance
equipped with a printer and infant seat was used. The balance
integrates repetitive weighings every 2 s: precision stated by the
manufacturer is ±0.05 g. The balance was placed on a level
surface and calibrated in the home by the researcher. Verbal
and written instructions were given and mothers demonstrated
their ability to use the balance. Mothers were asked to follow
their usual daily feeding routine noting any feedings in which
formula was used. For 7 ofthe 17 formula feedings, test weighing
was not possible and intake was measured as volume removed
from the bottle.
The 24-h milk intake was calculated by 1) summing the dif-
ference of the before and after weights for each feeding, 2) sub-
tracting the gram intake of the last feeding from the day’s total
(24 h plus 1 feeding) because intake from the next-to-last feed
satiated the infant until the time ofthe last feed, and 3) extrap-
olating to an exact 24-h period. The data used represented time
spans of24 ± 3 h.
Aletaholic control of WOflWfl ti’ith IDDIti
Postpartum metabolic control was determined by using
White’s classification ( I 9, 2 1). HbA1 at 3 and 42 d postpartum,
and fasting blood glucose (FBG) and blood glucose at 80 mm
after breakfast at each visit. Appropriate FBG concentrations
are 3.9-6.7 mmol/L (22). Blood glucose variability can be mea-
sured through continuous monitoring ofblood glucose patterns
and calculation of the mean amplitude of glycemic excursions
(MAGE) (23). Blood glucose at 80 mm after breakfast correlates
best with MAGE (24). Determination ofMAGE was not possible
in our study: therefore, the 80-mm postprandial glucose (PPG)
value was used. PPG should be < 8.9-10.0 mmol/L at 90 mm
(22). We considered an appropriate concentration for PPG at
80 mm to be 8.9 mmol/L.
Milk sample anali’.sis
Glucose and lactose were determined by using the model 27
industrial analyzer (Yellow Springs Instrument Co. Inc. Yellow
Springs, OH) (25). Total nitrogen was determined by the micro-
Kjeldahl method (26) by using the Tecator 1009 Digestion Sys-
tem and Tecator-Kjeltec System 1002 Distilling Unit (Hogan#{228}s,
Sweden). Conductivity was determined by using a model 35
Conductance Meter (Yellow Springs Instrument Co. Inc) cali-
brated with potassium chloride (27). Osmolality was determined
by freezing-point measurement with a model 5004 zOsmette
(Precision Systems. Inc. Natick, MA) calibrated with sodium
chloride (28). All milk samples were analyzed in duplicate.
Statistical anali’.sis
All statistical tests were done by using SAS (29, 30). When P
equalled 0.01 it is stated, otherwise P < 0.05 is assumed. Paired
t tests were used to determine differences between the left and
right breasts. Because breast milk composition did not differ
significantly between breasts, the average was calculated. A re-
peated-measures (split-plot) analysis ofvariance (ANOVA), using
the main effects of group. individual within group. time, and
group-by-time interaction, was used to determine group and
time differences for milk composition and intake by infants.
The protected least-significant difference test was used to make
contrasts between each pair ofgroup means (3 1). The assumption
ofcompound symmetry was checked by using the REPEA TED
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56
NEUBAUER ET AL
statement. Ifthe compound symmetry assumption was violated
(P < 0.05). the Huynh-Feldt conservative test was used to
check for interaction between group and time. For the co-
variates 80-mm PPG and time from last breast-feeding, a re-
peated-measures analysis ofcovariance was accomplished by
using S..1S PRO(’ GUt!.
The approximate F statistic was used to test the significance
of group-by-time interactions for breast milk intake. The ap-
proximate F statistic is calculated from a weighted average of
the between- and within-subject mean square error terms in the
ANOVA (3 1 ). For one-sided tests a power of 80. an effect size
of 1.2, and a significance level of0.05 were used (32). Pilot-study
data were used in the power calculations. Minimum sample sizes
for a power of 80 were exceeded. Spearman rank correlation
coefficients were used for correlations with White’s classification.
Pearson correlation coefficients were used for milk composition
and intake data.
Results
The groups did not differ concerning the time elapsed from
breakfast to the sampling of blood and milk. The women with
IDDM had a significantly longer time interval between the
mother’s last breast-feeding and when the milk sample was taken
compared with the control and reference women [least-squares
means (LSM) ± SEM: 3.76 ± 0.2, 2.56 ± 0.3, and 1.99 ± 0.3
h. respectively: F = 6. 15; df = 2, 73; P < 0.0 1 ]. All groups had
milk samples taken a minimum of 2 h after the last breast-
feeding. When the time interval from the last breast-feeding was
used as a covariate, it did not affect the milk-composition results.
The milk ofwomen with IDDM had significantly less lactose
(LSM ± SEM collapsed over time: 16 1.80 ± 3.66 mmol/L) than
the milk ofcontrol (174.87 ± 2.97 mmol/L) or reference (181.12
± 3.92 mmol/L) women (F = 7.00: df = 2, 70; P < 0.0 1) (Table
I). Milk lactose increased significantly over time to 42 d post-
partum (F = 76.22: df = 2. 70; P < 0.00 1). Breast milk lactose
was negatively and significantly correlated with breast milk con-
ductivity at 3 d postpartum for control and reference women (r
= -0.99). By day 7 postpartum all groups had negative and
significant correlations.
Women with IDDM had significantly higher milk total nitro-
gen at days 2 and 3 postpartum than did control or reference
women (F = 3.18: df 2, 68: P < 0.01). Total nitrogen was
negatively correlated (P 0.05) with milk lactose for women
with IDDM at days 3-84 postpartum, for control women through
day 14 postpartum. and for reference women only at day 2 post-
TABLE I
Breast milk composition*
Days postpartum
Component and
group 2
3 7 14 42 84
Lactose (mmol/L)
IDDMI
95.87 ± 7.13 161 59.87 ± 4.18 1171 163.34 ± 3.02 1291 178.01 ± 3.44 1241 185.58 ± 3.83 1201 188.16 ± 4.05 118]
(‘ontrol 130.81 ± 4.58 1141 163.01 ± 3.36 124] 175.84 ± 2.97 129]
I85.40 ± 3.38 [24] 92.49 ± 3.56 122] 201.65 ± 4.23 116]
Reference 142.80 ± 6.70 161 66.38 ± 4.74 II 1] 82.08 ± 4.74 11 I] 187.89 ± 4.74 II 1] 202.00 ± 4.74 [1 I] 205.60 ± 4.74 III]
Total nitrogen (gIL)
IDDM 7.78 ± ((.47 (3] 4.78 ± 0.23 1I3I
3.09 ± 0.15 125] 2.59 ± 0.16 124] 2.24 ± 0.18 120] 2.06 ± 0.19 118]
Control 5.46 ± ((.29 18] 3.49 ± 0.17 1221 3.02 ± 0.15 126]
2.49 ± 0.16 124]
2.16 ± 0.17 121]
.89 ± 0.21 114]
Reference 5.41 ± 0.3I [61 3.38 ± 0.25 [9] 2.94 ± 0.22 [I I] 2.49 ± 0.22 II I] 2.10 ± 0.22 (I I] 1.82 ± 0.22 [11]
Conductivity (t!(t
IDDM 0.28 ± 0.02 15] 0.31 ± 0.01 [17] 0.29 ± 0.01 [15] 0.25 ± 0.01 114] 0.25 ± 0.02 [11]
Control 0.32 ± 0.02 17] 0.29 ± 0.01 120] 0.25 ± 0.01 119] 0.20 ± 0.01 119] 0.21 ± 0.01 [16]
Reference 0.34 ± 0.02 18] 0.27 ± 0.01 II 1] 0.25 ± 0.01 [I II 0.21 ± 0.01 [10] 0.20 ± 0.01 [11]
Osmolality
(mOsmoIIkg)
IDDM 276.24 ± 9.09 [5] 297.98 ± 4.34 II6] 292.09 ± 4.55 1151 279.02 ± 4.86 [14] 286.89 ± 5.54 [II]
Control 287.16 ± 7.04 [7J 290.19 ± 3.92 [201 286.64 ± 4.22 118] 290.75 ± 3.96 [20] 298.09 ± 4.52 [16]
Reference 293.15 ± 6.01 18] 295.77 ± 4.95 [1 I] 296.95 ± 4.95 [I I] 292.79 ± 5.27 [10] 290.45 ± 4.95 [11]
Milk intake of
infants(gld)Il
1DDM 309.62 ± 32.37 [15] 426.05 ± 32.28 115] 575.29 ± 33.98 [14] 530.93 ± 39.47 [11]
Controi
455.46 ± 29.71 [17] 504.80 ± 35.69 1131 535.35 ± 36.04 [13] 51 1.95 ± 39.81 [II]
Reference 518.50 ± 38.20 [101 592.l7 ± 40.93 [9] 654.43 ± 38.20 [10] 673.72 ± 38.20 [10]
Milk and Ibrmula
intake of
infants (gJd(I
IDDM
329.89 ± 27.63 I15]
447.10 ± 27.55 [1S]** 624.70 ± 29.01 [14] 580.72 ± 33.69 [11]
Control
456.52 ± 25.36 [171 516.49 ± 30.46 [13] 542.44 ± 30.76 [13] 588.59 ± 33.98 [11]
Reference 528.12 ± 32.60 [101 595.36 ± 34.93 [9] 654.43 ± 32.60 [10] 684.33 ± 32.60110]
S Least squares means ± SEM. When group names are footnoted. group least-squares means collapsed over time are statistically different. ti in brackets.
ti: Significantly different from both control and reference: (P < 0.01, P < 0.05.
§ Data not available at 2 d postpartum.
II Data not available at 2 or 3 d postpartum.
1** Significantly different from reference: ‘P < 0.01. P < 0.05.
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IDDM
8
6
Control
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210
180
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90
210
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210
180
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point.
Reference
,f: I
2 3
DELAYED LACTOGENESIS AND DIABETES 57
partum. Correlations ranged from -0.57 to -0.76 for women
with IDDM and from -0.43 to -0.80 for control women; the
value for reference women was -0.87 at day 2 postpartum. We
graphed lactose and total nitrogen together to study their rela-
tionship as an index of lactogenesis. Although lactose and total
nitrogen intersect at similar concentrations for all groups, the
intersection occurs earliest in reference women, followed by
control. then women with IDDM (Fig I).
Breast-milk conductivity and osmolality did not differ among
the three groups. Milk conductivity decreased significantly over
time from 7 to 42 d postpartum (F = 21.12; df = 2, 54; P
< 0.00 1). Milk lactose (r = 0.36, 0.29), total nitrogen (r = -0.26,
-0.14) and conductivity (r = -0.37, -0.19) were significantly
correlated with feeding frequency for women with IDDM and
control women, respectively. Milk intake was significantly cor-
related with feeding frequency for women with IDDM at 14 (r
= 0.57) and 42 d postpartum (r = 0.8 1). for control women at
Days Postpartum
FIG I . Breast milk lactose (D) and total nitrogen (U), concentrations
for women with insulin-dependent diabetes mellitus (IDDM) and control
and reference women. Least squares means ± SEM, except when the
SEM is smaller than the diameter ofthe symbol. See Table 1 for number
of subjects. The point of intersection is used as an index of lactogenesis.
Lactogenesis occurred first in reference women, then in control women,
and finally in women with IDDM.
84 d postpartum (r = 0.72). and for reference women at 42 d
postpartum (r = -0.78).
Infants ofwomen with IDDM and control women consumed
significantly less breast milk (g/d) than did infants of reference
women (F = 4.69; df = 2, 43) (Table 1). Infant milk intake was
significantly correlated with breast milk lactose and conductivity
(negatively) for women with IDDM at 7 (r = 0.57, -0.81, re-
spectively) and 14 (r = 0.56, -0.76, respectively) d postpartum,
and at 7 (r = 0.68. -0.75, respectively) d postpartum for control
women. Milk intake of infants of women with IDDM was also
significantly negatively correlated with total nitrogen at 7 (r
= -0.64) and 14 (r = -0.53) d postpartum. Infants of women
with IDDM consumed significantly less breast milk and formula
combined than did infants ofcontrol women at 7 d postpartum
and of reference women at 7 and 14 d postpartum (F = 2.58;
df= 2, 43).
The mean HbA1 concentration at 3 and 42 d postpartum
was within normal limits for women with IDDM: however, it
was significantly higher than in the other groups (LSM ± SEM:
IDDM 5.54 ± 0.1 1%, control 4.16 ± 0.10%, and reference 4.33
±0.l3%;F= l4.17:df= 2, 71;P<0.00l). The majority(53%)
of the women with IDDM had an FBG 6.7 mmol/L at all
times. Women with IDDM had significantly higher 80-mm PPG
concentrations than did control or reference women (LSM
± SEM: 13.6 ± 0.3. 5.6 ± 0.3, and 5.7 ± 0.4 mmol/L, respec-
..:. tively: F = 82.12; df = 2. 74; P < 0.001). The average PPG
4 Q, concentration for women with IDDM ranged between I 1.6
-:: ± 0.7 and 1 5.6 ± 0.7 mmol/L throughout the study. A minimum
2 of 72% of these women had values > 8.9 mmol/L at each time
White’s classification was significantly correlated with total
8 milk nitrogen at day 3 postpartum (r = 0.38) and negatively
with lactose at days 7 (r = -0.25) and 84 postpartum (r = -0.42).
6 There were no significant correlations between HbA and milk
L composition. FBG correlated significantly with total nitrogen at
: 2 d postpartum (r = 0.99). Women with IDDM with an FBG
4 .‘ > 6.7 mmol/L had greater milk conductivity at 7 d postpartum
> than did women with IDDM with an FBG 6.7 mmol/L; they
/ 2 also had greater milk conductivity than control or reference
women(F= 3.17;df= 3,39:P<0.00l).
Women with IDDM with a PPG > 8.9 mmol/L had total
milk nitrogen at 2 d postpartum and osmolality at 3 d postpartum
8 significantly higher than values for women with IDDM with a
: PPG 8.9 mmol/L and control and reference women. Milk
6 o composition ofwomen with a PPG 8.9 mmol/L did not differ
significantly from that of control or reference women. Infants
4 - ofwomen with PPG > 8.9 mmol/L had significantly less milk
.- intake than did infants ofwomen with a PPG 8.9 mmol/L at
C (F = 5.2 1: df = 3, 38: P < 0.0 1) and 14 (F = 3. 18: df = 3, 33)
7f’ 2 d postpartum. Milk lactose ofwomen with an FBG > 6.7 mmol/
7 L or a PPG > 8.9 mmol/L was consistently lower at 2. 7, and
14 d postpartum (NS).
When PPG was used as a covariate, infants of women with
IDDM had significantly less milk intake than did the reference
infant group at 7, 14, and 84 d postpartum and than did the
control infant group at 84 d postpartum (F = 2.27; df = 2134).
Without the covariate, group means collapsed over time were
significantly different. The adjusted group means for milk intake
for women with IDDM increased at 7, 42, and 84 d postpartum
but remained essentially unchanged for the other groups.
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58 NEUBAUER ET AL
Discussion
A delay in the initiation of lactation in women with IDDM
is indicated by the lower milk lactose and lower breast milk
intakes oftheir infants. Arthur et al (4) also found that mothers
with IDDM had a delay of 28 h for milk lactose to reach com-
parable concentrations found in women without diabetes.
The higher nitrogen content in the milk ofwomen with IDDM
at 2-3 d postpartum in the present study also suggests delayed
lactation. Kulski and Hartmann (5) found a dramatic decrease
in milk total protein consistent with the onset of lactogenesis.
To compare our results with theirs. we converted total protein
to total nitrogen. using a factor of 6.25 assuming that protein
nitrogen comprises 87% oftotal nitrogen at days 2-3 postpartum
(33). In Kulski and Hartmann’s (5) study. the derived milk total
nitrogen peaked at I 1.4 g/L 30 h after delivery and decreased
by more than halfto 4. 1 g/L by 50 h postpartum. If lactogenesis
were “on time,” the total nitrogen for the women with IDDM
(7.8 g/L) should be far less at 45 h from delivery. The total
nitrogen ofcontrol and reference women followed a similar pat-
tern of decline as that found by Kulski and Hartmann. Breast
milk nitrogen ofwomen with IDDM was not similar to that of
the other groups until 7 d postpartum.
The negative correlation between lactose and total nitrogen
for all groups at 2 d postpartum is consistent with lactogenesis.
Others have documented similar negative correlations of lactose
and whey proteins (5) or total protein (34) as estimates of the
timing oflactogenesis. In the present study the lactose and total
nitrogen contents for the reference women were correlated only
at day 2 postpartum. indicating subsequent establishment of
lactation and corroborating the findings reported previously (5.
34). The negative correlation existed the longest for women with
IDDM. indicating a delay in lactogenesis.
Saint et al (3) also found a positive correlation between lactose
and milk yield and a negative correlation between total protein
and milk yield to be consistent with lactogenesis. The lack of
significant correlations between lactose or total nitrogen and
breast milk intake for reference women further suggests that
lactogenesis likely occurred before the time when breast milk
intake was first studied at das 7 postpartum. In contrast, signif-
icant correlations still existed for control women at 7 d post-
partum and for women with IDDM at 14 d postpartum. which
suggests that full lactation could not have been established until
after this time.
Before lactogenesis. the paracellular pathway is leaky and so-
dium, chloride. and water pass into the milk diluting lactose
and maintaining osmolality (35). This additional sodium and
chloride would increase milk conductivity. However, as lactose
increases with established lactation and the paracellular pathway
no longer leaks. sodium and chloride, and consequently con-
ductivity. decrease. Delayed lactation for women with IDDM
based on milk conductivity is suggested because a negative cor-
relation with lactose was not established until day 7 postpartum
and with intake by infants until day 14 postpartum.
The lack ofearly maternal attachment associated with cesarean
section deliveries may be a factor in the delayed lactogenesis for
women with IDDM (36). Kulski et al (37) found no difference
in milk lactose as a result ofcesarean section delivery but suckling
began within 12 h after delivery in their study. Women with
IDDM first breast-fed their infants at 26. 1 ± 2.8 h after delivery
( 19): therefore. lack of early breast stimulation may have influ-
enced this delay.
It is interesting that feeding frequency was not correlated with
milk composition or milk intake for reference women but
was for women with IDDM and control women. Similarly,
Nommsen et al (38), in their longitudinal study of healthy, cx-
elusively breast-feeding women (< 120 mL/d of other milk or
formula). found that breast-feeding frequency was not significant
in the regression equations relating to macronutrient milk com-
position at 3. 6, 9. or 12 mo postpartum when controlled for
milk production. Others have also noted no relationship between
breast-feeding frequency and milk intake (39-41). It may be
that feeding frequency is not an issue for healthy breast-feeding
mothers with well-established milk output. However, for women
with multiple problems related to their prenatal care and puer-
perium recovery, such as the women in our study with IDDM
and control women, feeding frequency may be an important
determinant of breast-feeding success.
A delay in lactogenesis in women with IDDM is postulated
on the basis ofa comparison with the milk-composition values
of the reference women. Milk lactose values for the reference
women were similar to those reported at 48-72 h postpartum
(3. 7), 42 d postpartum (42), and 3 mo postpartum (38. 43).
They were slightly higher than those previously reported for milk
from our laboratory: 173 mmol/L at 42 d postpartum and 188
mmol/L at 84 d postpartum (44). Different analytical methods
may explain this because in the earlier study an enzymatic
method from Boehringer-Mannheim Biochemicals was used
(44). Our reference women had slightly lower milk lactose con-
centrations at 7 and 14 d postpartum than did multiparous
women (45) and women in developing nations (46, 47).
The milk total nitrogen concentrations ofcontrol and reference
women agreed with results ofother investigators at 1-3 (33, 48),
7-20 (44. 48. 49), and 90-105 d postpartum (44. 47-49).
L#{246}nnerdal et al reported slightly higher total nitrogen in privi-
leged women in Ethiopia (47) and Sweden (50) at 0.5-1.5 mo;
however, exact comparison is difficult because different time
periods were reported. The breast milk lactose and total nitrogen
concentrations of women with IDDM were similar to values
reported in the literature (12. 51).
The remarkable stability ofmilk osmolality found in the pres-
ent study confirms the findings ofsome researchers (28, 52, 53),
but slightly lower (54) or higher (55) osmolality was found by
other investigators. As the secretion of lactose increases to
amounts consistent with established lactation, the ionic concen-
tration decreases to maintain milk isoosmotic with plasma (35).
The similarity among the groups in milk osmolality and con-
ductivity suggests that even though women with IDDM had
significantly lower milk lactose, the ionic concentration was not
significantly altered.
Milk-intake data for infants ofwomen with IDDM from other
studies is not available. Breast-milk intake ofour reference group
was o50 g/d below that reported by Neville et al (39) for the
same infant ages in exclusive breast-feeders. All oftheir subjects
and 50% of our subjects were multiparous. If the multiparous
women breast-fed previously, then prior lactation experience
could account for the larger intakes (56). Several investigators
have reported data at 84-90 d postpartum. Our 84-d value of
674 ± 38 g/d falls at the lower limit of values reported: 676 to
81 1 ± 133 g/d (38, 43. 57). Differences can be attributed to the
large variation in breast milk intake (43), use of a less-accurate
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DELAYED LACTOGENESIS AND DIABETES
59
1 . Whichelow MI. Doddridge MC. Lactation in diabetic women. Br
Med I 1983:287:649-50.
pediatric balance (43). or insensible water loss during breast-
feeding (38).
Although infants of women with IDDM received more for-
mula throughout the study than did the infants ofcontrol and
reference women, group differences in breast milk intake are
only offset by the higher formula intake at 42 and 84 d post-
partum. One cannot determine whether the infants of women
with IDDM who were given formula actually needed a supple-
ment. Perhaps if their mothers had not offered formula. the
infants’ demand would have stimulated increased breast milk
production to a degree that would have satisfied their appetites.
Alternatively. without the formula. their nutrition might have
been compromised.
The issue of metabolic control during lactation in women
with IDDM is not clearly defined. All criteria used to measure
metabolic control suggested that good metabolic control is an
important determinant ofsuccessful lactation, in terms of “nor-
mal” milk composition. in women with IDDM. However, no
one criterion is a predictor ofchanges in milk composition.
Women with IDDM with a higher White’s classification, and
therefore more severe diabetes and/or poorer metabolic control
(as measured by HbA1, FBG. or 80-mm PPG). were more likely
to have delayed lactogenesis. This is indicated by the negative
correlations between White’s classification and lactose and the
positive correlations between both White’s classification and
FBG and total nitrogen at 2-3 d postpartum. As initially hy-
pothesized. women with IDDM with good metabolic control
had milk composition similar to that of control and reference
women, with respect to the nutrients measured in this study.
However, women with elevated FBG or 80-mm PPG had higher
total nitrogen at day 2 postpartum: osmolality at day 3 post-
partum: conductivity at day 7 postpartum: lower lactose at days
2. 7. and 14 postpartum: and lower infant milk intake at days
7. 14. and 84 postpartum. which suggests that the delay in lac-
togenesis was influenced by metabolic control. The increase in
the breast-milk intake of infants of mothers with IDDM when
the groups were equalized for 80-mm PPG further substantiates
this conclusion.
Women with IDDM were able to breast-feed and despite sig-
nificant differences in breast milk lactose and total nitrogen con-
centrations, milk composition for these nutrients was within
accepted ranges. There was a delay in lactogenesis for women
with IDDM, indicated by lower milk lactose. higher total nitrogen
at 2-3 d postpartum. delayed intersection oflactose and nitrogen
when graphed (Table 1). a negative correlation between lactose
and nitrogen. a negative correlation between both conductivity
and total nitrogen and intake by infants. and lower milk intake
by infants ofwomen with IDDM. This delay was correlated with
poor metabolic control. 13
We thank the breast-feeding mothers who participated in this study
and their families: other members ofthe field collection team, Karin M
Ostrom and Maureen Murtaugh: other laboratory staff. Marjorie B
Jackson and Sara Collins Couch: Constance M Capacchione and Jeffrey
R Backstrand for data management support: the hospital personnel who
were so cooperative and helpful in executing the study: and Lindsay H
Allen for review of the study design and thesis manuscripts.
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