Postpartum Consequences of an Overlap of Breastfeeding and Pregnancy
Objective
Despite
cultural pressure to wean when a new pregnancy occurs, some women
choose to continue breastfeeding. We determined the effect of an overlap
of lactation and late pregnancy on breastfeeding and growth in early
infancy.
Methods
We
studied 133 Peruvian pregnant women who were ≥18 years of age, had a
child <4 years old, and who then had a vaginal birth with a healthy,
normal weight infant. Of the 133 women, 68 breastfed during the last
trimester of pregnancy (BFP), and 65 had not breastfed during pregnancy
(NBFP). On day 2 and at 1-month postpartum, 24-hour intake of breast
milk and other liquids was measured. Twice weekly home surveillance
documented infant morbidity and dietary intakes. Anthropometry was taken
at birth and at 1 month. Maternal anthropometric, health, and
socioeconomic status data were collected pre- and postpartum.
Results
Pregnant
BFP mothers breastfed 5.3 ± 4.3 times/day. BFP and NBFP infants did not
differ in breastfeeding behavior or in colostrum intake on day 2. BFP
infants breastfed longer per feed and per 24 hours (35.2 minutes/24
hours) than did NBFP infants; however, 1-month intakes per feed tended
to be lower among the BFP infants. After controlling for confounders,
BFP infants gained 125 g less than did NBFP infants (about 15% of mean
weight gain). A sustained decline would result in a −0.7 z score change in weight-for-age by 6 months.
Conclusions
A
lactation-pregnancy overlap had a negative effect on early infant
outcomes. Additional studies are needed to determine whether the effect
continues past 1 month of age.
Keywords: breastfeeding, pregnancy, overlap, breast milk volume, weight gain, infant feeding, Peru
ABBREVIATIONS: BFP,
breastfed during pregnancy; NBFP, did not breastfeed during pregnancy;
BMI, body mass index; SES, socioeconomic status; CI, confidence
interval; OR, odds ratio
Many
women throughout the world breastfeed for as long as possible to give
their children the nutritional, immunologic, and emotional benefits of
breastfeeding. When lactation overlaps a new pregnancy, some women
choose not to wean their toddlers, although there may be strong cultural
taboos against continuing to breastfeed.1, 2
The practice of continuing to breastfeed during pregnancy has been
reported among US women but might not be discussed with health
professionals because of anticipated criticism of the practice.3–5
Breastfeeding during pregnancy is more common in some low-income
countries than in the United States because shorter birth intervals
increase the likelihood of a pregnancy-lactation overlap.
It has been suggested that an overlap could produce suboptimal outcomes for both pregnancy and subsequent lactation.6–8
Dairy research has demonstrated that a complete overlap of lactation
during pregnancy dramatically compromises the total production of mature
milk during the next lactation period.9–14
A dry (nonmilking) period of approximately 2 months before calving is
usual in the dairy industry. This is the first human study to provide
data on the association between the practice of lactating through late
pregnancy and breastfeeding and growth outcomes of young infants.
METHODS
Participants
The
study was conducted in a poor periurban community of approximately 800
000 on the outskirts of Lima, Peru. The inclusion criteria for mothers
were: 1) pregnant; 2) ≥18 years of age; 3) multiparous and living with
her child <4 years old; 4) without apparent indicators for elective
cesarean section; and 5) either continuing to breastfeed into the third
trimester or never breastfed during this pregnancy. Routes to identify
possible participants were community census, local prenatal health
service registers, and referrals. Between July 1998 and January 2000,
3417 pregnant women were identified. Of these, 601 women were not
located at home, and 27 women declined to participate in a screening
interview. Field workers screened 2789 pregnant women, and 727 met all
of the inclusion criteria: 170 women breastfed their older children
during the third trimester of pregnancy (BFP) and 557 women had not
breastfed at all during the present pregnancy (NBFP). Breastfeeding was
confirmed by direct observation; date of weaning was obtained from those
mothers who had weaned during the third trimester and before
enrollment.
Postpartum follow-up was confined to women who
gave birth to an infant who was a vaginal delivery, full-term (>37
weeks’ gestational age), healthy birth weight (>2500 g), and with no
birth defects or complications that would hinder breastfeeding. Of the
170 enrolled BFP women, 70 mother-infant pairs were followed after
birth. Reasons for no postpartum follow-up included refusal (N = 40), moved or worked (N = 12), mother not available within 48 hours of birth (N = 13), birth problems (N = 19), and other (eg, twins, older child with problems; N = 16).
Of
the 557 NBFP women enrolled during pregnancy, 67 were followed up.
Probable data of delivery was recorded for all NBFP mothers. For each
BFP infant born, a NBFP woman was selected at random from the pool of
women scheduled to give birth that month. The first selected NBFP woman
who met the postpartum criteria was included. The reasons for no
follow-up were refusal (N = 174), moved or worked (N = 40), not randomly selected (N = 71), not available within 48 hours of birth (N = 99), birth problems (N = 54), and other (N
= 52). Of the 137 infants who were studied on day 2 postpartum, 133
infants had a repeated study at 1 month of age. Two BFP and 2 NBFP
infants had no repeat study because of refusal (N = 2) and moving (N = 2). This analysis is based on the 133 infants with observations for both days.
Comparison of Included and Excluded Families
The
included BFP families had some indicators of a better economic status
(eg, housing quality) than the excluded BFP families. The included NBFP
mothers were significantly more likely to be younger, born in the
mountains, and live with fewer adults as compared with excluded NBFP
families. Other family demographic, socioeconomic, and obstetric data
that were collected during pregnancy did not differ.
Data Collection
Obstetric History and Birth
At
screening, all pregnant women were interviewed about their obstetric
history and previous breastfeeding experience. Morbidity data were
gathered twice monthly for all enrolled women. Relevant delivery and
birth information was collected from clinical records when available and
from mothers. For deliveries at health facilities, dystocia (abnormal
duration of labor) was defined by practitioners, using the World Health
Organization’s partograph to monitor cervical dilatation and fetal
descent.15 All home births were assumed to have involved normal labor.
Breastfeeding Behavior
Once
a month during pregnancy, BFP mothers recorded their toddlers’ feeding
frequency or the date of weaning. After birth at twice-weekly home
visits, mothers recalled their breastfeeding practices of the previous
days, including whether the infant was breastfed by another woman and
whether the mother breastfed another child.
Twenty-four-hour
breast milk intakes and duration of feeds of all infants were measured
twice: day 2 (41.7 ± 5.7 hour) and 1 month (33 ± 3 days). Milk intake
was measured by the test weighing method,16
weighing the infant before and after each feed, using an electronic
digital balance sensitive to 1 g (Mettler Toledo Model SB/16 000,
Columbus, OH). Total milk intake was corrected for a 3% insensible water
loss.17
On both days, only 0.1% of feeds were not weighed because the mother
was not at home at the time of the feed. The missed values were imputed
using separate multiple regression equations that estimated intake per
feed by time since last feed, duration of the missed feed, and child
identifier. Milk intake was expressed as g/feeding and g/24 hours.
Intake of Other Liquids/Foods
Nonbreast
milk liquids that were consumed during the 24-hour observation period
were weighed. Information on reported intake for all other days was
collected at twice-weekly visits.
Anthropometry
Birth
weights and lengths were collected from health facilities when
available. A similar number of BFP and NBFP mothers gave birth at home,
and their infants were weighed and measured by the study staff within 3
days. For clarity, both of these measurements are referred to as the
first weight or length. At 1 month of age, infants were measured in
triplicate without clothes in the field office. Weight was measured on a
digital electronic infant scale (Soehnle-Waagen GMbH and Co, KG,
Murrhardt, Germany) sensitive to 10 g. Length was measured to the
nearest 0.1 cm with a locally made rigid length board. Head
circumference was measured to 1 mm with nonstretchable tape measures
(Lasso, Child Growth Foundation, London, United Kingdom).
Maternal
mid-arm and calf circumferences were measured pre-and postnatally to a
precision of 1 mm with the same nonstretchable tape measurer mentioned
above. Weight and height were measured at 1-month postnatally, using a
Seca adult beam balance with a precision of 100 g and a locally-made
stadiometer with a precision of a 0.1 cm. Body mass index (BMI)
(weight/height2) was calculated. Field workers were standardized.18
Morbidity
Maternal
reports of daily symptoms of infants and any treatment were recorded
twice weekly for the first month. Stool character and frequency as well
as general and respiratory symptoms were recorded along with maternal
illness and treatment. A diarrheal day was a day with 3 or more
liquid/semiliquid stools in 24 hours. A dichotomous variable of ever
having diarrhea was developed. Prevalence of diarrhea and cough in the
infant and any maternal illness was calculated. Other symptoms were
infrequent (<6% of days observed) and, therefore, not considered
here.
Socioeconomic Data
Socioeconomic
data on the quality of housing, hygiene, possessions owned, and
education and employment of family members were collected at the
screening interview and day 2 postpartum.
Data Analysis
Mean group differences for continuous variables were tested with the Student t
test and analysis of variance; Kruskal-Wallis 1-way analysis of
variance was used for variables with nonnormal distribution. Frequency
differences were tested with the χ2 goodness-of-fit test.
Multiple linear regression models were used to estimate the effect of
breastfeeding late in pregnancy on day 2 and 1-month breast milk intake
and 1-month growth. Logistic regression was used to estimate the effect
of an overlap on the risk of very low (<25th percentile) milk intake
and growth. Both models controlled for confounding factors including
sex, age, first weight, feeding behaviors (duration and frequency of
feeds, breastfed by another woman, hours postpartum), and maternal
characteristics (age, parity, pregnancy complication, anthropometric
measurements). With birth weight or length in an equation predicting
1-month weight or length, the other coefficients reflected their effects
on the corresponding increment from birth. Morbidity (eg, prevalence of
diarrhea and cough) and socioeconomic status (SES) variables were not
significant predictors of the milk and growth outcomes. The effects of
BFP on milk intake and growth outcomes in the models discussed here were
unchanged when analyses were rerun without 10 children who received
breast milk from other mothers.
All analyses were conducted with SYSTAT version 10.19 Data are presented as the mean ± standard deviation and significance for all 2-tailed probability tests was set at P
< .05, unless otherwise indicated. This study was approved by the
Human Subjects Research Office at Iowa State University, University of
Alabama at Birmingham, and the Ethics Committee at the Instituto de
Investigación Nutricional; written informed consent was obtained.
RESULTS
Family Baseline Characteristics
NBFP families appeared poorer than BFP households (Table 1).
NBFP houses were made of lower quality materials and were less likely
to have piped water and a functioning sewage system. Field workers
observed human fecal matter on the floor in 3 times more NBFP than BFP
homes; however, this did not reach significance.
Baseline Family Socioeconomic and Demographic Characteristics by Practice of Breastfeeding During Pregnancy (n = 133)
Maternal and Infant Characteristics
Baseline
BFP and NBFP mothers were similar in age and education (Table 2).
Only 2 women (1 BFP and 1 NBFP) worked in the formal sector. Compared
with NBFP mothers, twice as many BFP mothers were born on the coast and
lived about 3 years longer in Lima. Although there were no differences
between groups in parity, the last interbirth interval was longer for
NBFP mothers than BFP mothers, as demonstrated by the 10-month
difference in the age of the last child.
Baseline, Prenatal, and Postpartum Maternal Characteristics by Practice of Breastfeeding During Pregnancy (n = 133)
Prenatal, Birth, and Postpartum Characteristics
About three fourths of all women attended a health facility for prenatal care (Table 2).
NBFP mothers were more likely than BFP mothers to seek prenatal care at
the governmental health centers rather than private facilities (75.8%
vs 55.9%). There were no group differences in prepartum anthropometric
measurements, reported pregnancy complications, or smoking during
pregnancy (2 BFP and 2 NBFP). BFP mothers breastfed their toddlers 5.3 ±
4.3 (median: 4) times per day. Fourteen mothers breastfed >5 times
during the daytime; the maximum frequency reported was 17 feeds/day.
Of
those who gave birth in a health facility, abnormally prolonged labor
(dystocia) tended to occur more often among the BFP than the NBFP
mothers (Table 3). Other birth and newborn characteristics were not different between groups.
Birth Events and Newborn Characteristics by Practice of Breastfeeding During Pregnancy
There
were no differences in postpartum anthropometry or prevalence of
maternal illness in the first month postpartum. Mothers reported being
ill <10% of the first 30 days postpartum.
Breastfeeding Characteristics
Breast Milk Intake
There was a wide range of 24-hour intake of colostrum (2g–570 g; Fig 1).
When intake was adjusted for time after birth of initiation of study,
the higher intake of BFP infants than NBFP infants (195.3 ± 110.7 vs
175.1 ± 110.7 g/24 hour, P = .13; respectively) did not reach
significance. There were also no group differences in frequency or total
duration of breastfeeding over the 24 hours. Mothers breastfed a mean
of 20.7 ± 5.1 times for a total of 305.8 ± 116.9 minutes.
Infants’
24-hour intake of their mothers’ breast milk by presence of a
breastfeeding-pregnancy overlap and day of observation. Upper and lower
limits of the box represent the 25th and 75th percentile values; the
horizontal line within ...
At
1 month of age, the number of feeds per 24 hours decreased to 16.9 ±
3.4. In contrast with the observation shortly after birth, BFP mothers
breastfed for 35.2 minutes (95% confidence interval [CI]: 11.5–58.9
minutes) longer than NBFP mothers, for a mean total time of 213.8 ± 80.0
versus 178.6 ± 56.4 minutes (P < .01), respectively. The
average duration of a feed was significantly longer among the BFP than
the NBFP mothers (12.4 ± 3.9 vs 10.9 ± 2.9 minutes, respectively; P < .01). This increased time did not translate into higher milk intakes (Figs 1 and and2).2).
BFP as compared with NBFP infants had about a 9% decline in intake per
feed that tended to be significant (46.2 ± 14.6 vs 50.4 ± 11.2 g/feed; P = .06) and about an 8% lower total milk intake (765.5 ± 212.3 vs 810.5 ± 161.9 g/24 hour; P = .17).
Infants’
mean intake per feed of their mothers’ breast milk at 1 month by
presence of a breastfeeding-pregnancy overlap. Upper and lower limits of
the box represent the 25th and 75th percentile values; the horizontal
line within the box ...
Breast Milk From Other Mothers
Ten
infants were observed also to be breastfed by another woman, 6 on day 2
(4 BFP and 2 NBFP) and 4 (all BFP) at 1 month. The odds ratio (OR) of a
BFP infant receiving milk from another mother at either observation
point was 4.2 (P = .06). During both observation days, the
range of milk consumed from other mothers was wide: 1 g to 105 g
(median: 30.4 g) on day 2 and 14 g to 209.1 g (median: 54.6 g) at 1
month. When intakes of breast milk from the infant’s mother and other
women were summed, the difference in milk intake at 1 month between BFP
and NBFP infants was attenuated slightly (770.4 ± 208.4 vs 810.5 ± 161.9
g/24 hour; P = .22). The results (regression coefficients and
significance levels for breastfeeding during pregnancy) for breast milk
intake and growth discussed below were similar with and without the data
from these 10 children who received milk from another woman.
Tandem Breastfeeding
About one third of the BFP mothers breastfed another child in addition to the newborn on day 2 (N = 24; 35.3%) and at 1 month (N
= 27; 39.7%) postpartum. On day 2, only 1 NBFP mother breastfed another
infant (total = 10.3 g). Milk intakes of the other child ranged from 0
to 384.2 g on day 2 and 0 to 405.8 g at 1 month. When milk intake of the
other child was considered as part of total milk production, the
difference between BFP and NBFP mothers was reduced. The mean 1-month
intakes of infants increased progressively from BFP/no tandem
breastfeeding (762.5 ± 232.4 g/24 hour), BFP/tandem breastfeeding (768.6
± 192.3 g/24 hour), to NBFP (813.0 ± 161.8 g/24 hour), demonstrating
that tandem feeding did not account for the low milk intakes of BFP
infants.
Use of Other Liquids
Exclusive
breastfeeding was short-lived in this community. Ten percent (10.3%) of
the BFP infants and 6.2% of the NBFP infants received nonbreast milk
liquids during the first 24 hours of life, including sugar water, other
milks, and teas. By 1 month, 31.6% of all infants had been given other
liquids (32% of liquids were teas or water; 68% were other milks), with
no group difference in use. However, the BFP as compared with the NBFP
infants had a higher total number of days when other liquids were
offered (9.4 ± 7.5 days vs 4.4 ± 3.0 days; P < .001) and higher total 30-day intake of teas and water (3.5 ± 9.4 vs 0.7 ± 2.0 fl oz).
One-Month Infant Characteristics
Morbidity
There
was little diarrheal morbidity during the first 30 days of life; 25
mothers reported that their infants had at least 1 day of diarrhea
(about 20% in both groups). Significantly more BFP than NBFP infants had
a cough for >7 days (35.3% vs 20.0%).
Growth Outcomes
Complete
weight data were available for 66 BFP and 64 NBFP infants; length data
were available for 63 BFP and 57 NBFP infants. The infants had similar
first weights. BFP infants gained 170 g less (95% CI: −0.308 to −0.031)
than NBFP infants over the first month of life (Fig 3),
a 14% difference in weight gain. By 1 month of age, there was a
nonsignificant mean difference of −118 g (95% CI: −313 to −77) in
attained weight of BFP as compared with NBFP infants. There was no group
difference in length gain (BFP gained 4.6 ± 1.4 and NBFP gained 4.7 ±
1.5 cm), attained length, or head circumference at 1 month.
One-month
weight (solid) and length (hatched) gain of study infants by presence
of a breastfeeding-pregnancy overlap. Upper and lower limits of the box
represent the 25th and 75th percentile values; the horizontal line
within the box represents the median. ...
Models to Estimate Breast Milk Intakes From Infant’s Mother
Day 2
Day 2 breast milk intakes were associated with several factors (Table 4).
Milk intake decreased about 25 g for each 5-year increment of maternal
age and 3 g per 10 additional minutes of breastfeeding. Intake increased
6.5 g per 100-g increase in the first weight. Receiving breast milk
from another woman was strongly associated with a lower intake (−96 g)
from the infant’s own mother. BFP was not associated with day 2 intake
when controlling for these above factors and time of initiation of the
study.
Multiple Linear Regression Models for 24-Hour Breast Milk Intake on Day 2 and at 1-Month Postpartum*
One Month
Parity significantly modified the effect of a breastfeeding-pregnancy overlap on 1-month milk intake (Table 4).
Holding the other explanatory variables constant, for each increase of 1
birth, there was an additional 116-g reduction in milk intake among BFP
infants but only a 17-g reduction among NBFP infants (interaction term;
P = .01).
Milk intake was positively associated
with the number of feeds but was negatively associated with duration.
The first weight, an indicator of child requirements, was the primary
determinant of milk intake; a 1-kilo increase was associated with a
152-g increase in intake. Finally, maternal report of complications
during pregnancy was positively associated with milk intake; the
explanation of this relationship is not clear. Tandem breastfeeding,
receiving milk from another mother, and intake of nonbreast milk liquids
did not explain any additional variance.
The
risk of a very low breast milk intake (<25th percentile of the study
population) at 1 month was fivefold higher among those infants who were
breastfed also by another women (OR: 5.3; P = .01). These data
do not indicate if this practice negatively affected maternal
production or was in response to a previous low production.
Models to Explain 1-Month Infant Weight Gain
After
controlling for other factors, the practice of breastfeeding throughout
pregnancy was associated with a decrease in 1-month weight gain (Table 5).
Holding the continuous explanatory variables at their mean, a BFP
infant gained 125 g less (95% CI: 8–241) than NBFP infants, or about 15%
of National Center for Health Statistics mean weight gain.20 A sustained decline of this magnitude would result in a −0.7 z score change in weight-for-age by 6 months of life.
Multiple Linear Regression Models for 1-Month Weight (kg) and Length (cm) Gain
The
negative effect of BFP on weight gain was amplified by an increase in
maternal calf circumference (an additional −53 g/mm increase in calf
circumference among only BFP infants). For example, for a mother with a
calf circumference equivalent to the 75th percentile (34.4 mm), the
weight gain in a BFP infant was 175 g less than that of an equivalent
NBFP infant, almost 20% of National Center for Health Statistics mean
weight gain. Maternal calf circumference had a significant positive
correlation with maternal age and BMI at 1 month (r = 0.25 and
0.75, respectively) and may be functioning as a proxy of nutritional
stress, age, or other related biological factors.
Intake
of bovine milk had a negative effect on weight gain. Lower weight gain
was also associated with being female, higher parity, and younger infant
age.
Controlling for infant’s age, the
risk of a very low weight gain (<25th percentile value of the study
population; <0.9 kg) tended to double for BFP infants (OR = 2.193; P = .077) and was threefold higher for females (OR = 2.8; P
= .03). Other feeding practices, such as tandem feeding, breastfeeding
from another woman, or use of nonbreast milk liquids, did not affect the
total weight gain or the risk of a very low weight gain.
Models to Explain 1-Month Infant Length Gain
Similar models were developed for length gain (Table 5).
Length gain was positively associated with infant’s age and tended to
increase with increased breast milk intake on day 2. BFP as well as
other breastfeeding practices did not explain any additional variance in
length gain.
No variables were
significant explanatory factors for the risk of very low (<25th
percentile value of the study population; <3.55 cm) length gain.
DISCUSSION
Lactation during pregnancy is known to have adverse effects on milk production in cows.9–14
The present study is the first human study to document a negative
effect of an overlap of lactation and late pregnancy on the
breastfeeding and growth success of the subsequent infant. The magnitude
of the effect on weight gain is cause for concern. A sustained 15%
decline in expected weight gain would move an infant born at the 50th
percentile to under the 25th percentile weight-for-age by 6 months of
age.
The primary limitation of the study is group
self-selection. That is, mothers chose whether they were BFP or NBFP;
they were not randomly assigned to a feeding group. Without the benefit
of randomization, it is possible that other confounding factors explain
our results. For example, if SES were a confounder and the true
determinant of poor growth among the BFP children, then one would expect
the BFP families to be poorer than the NBFP families. However, a number
of indicators suggested that the SES was lower in the NBFP families. It
is not clear how the group differences in maternal characteristics,
such as place of birth, would affect breastfeeding success unless they
reflect breastfeeding support networks. Shorter interbirth intervals
among BFP mothers may reflect decreased recuperation of maternal stores.21,22 Milk production may be reduced when maternal diet is extremely limited23,24;
however, observed social conditions and maternal BMI levels (mean value
in the range of overweight) do not support this mechanism. In addition,
there were no group differences in maternal anthropometric indicators
pre- or postnatally. It is possible that BFP is a proxy for other
maternal psychosocial factors, not measured, that influenced successful
mothering and, ultimately, growth.
Butcher (cited in reference 11)
estimated a reduction of 585 kg of milk over the course of the
lactation in cows that were milked up to 5 to 20 days before
parturition. The mechanism of reduction of milk production in cows is
not well understood; possibly, with an inadequate nonmilking period
before birthing, there is insufficient involution and subsequent
rejuvenation of the mammary secretory cells. Species vary in the amount
of involution that naturally occurs; those with longer cycles and a
functional luteal phase normally retain some of the alveolar structure.11,14 The importance of this mechanism in humans is not well understood.
Healthy infants self-regulate intake to meet their needs.25
Generally, a reduced milk intake in BFP infants could have 3 causes: 1)
maternal behaviors that reduce infant access to milk, 2) limited
maternal production, and/or 3) reduced infant demand. The similar
feeding frequency and increased duration among BFP infants are
inconsistent with the first explanation. However, the data were
collected at 1 time point and may not reflect feeding behaviors over the
entire month. Also, although access was similar, BFP infants may have
been less successful at extracting milk or expending more energy doing
so. Studies on feeding mechanisms are needed.
Second,
dairy research would suggest that the lower intakes were related to
lower milk production. However, when total milk production was
calculated, those BFP mothers who had additional stimulation because of
tandem breastfeeding were able to produce an equal amount of milk as
NBFP mothers, suggesting that milk production was not a limitation. The
selection bias for tandem breastfeeding is not known. Women who
perceived inadequate milk production may have chosen not to tandem
breastfeed.
Finally, there are no data to assume a lower
demand for milk from the BFP infants. No infant was low birth weight or
premature, or had any conditions that would hinder breastfeeding. BFP
infants had slightly higher rates of symptoms of upper respiratory tract
infections. Difficulty in breathing associated with illness could
hinder infants breastfeeding; however, previous studies have
demonstrated only a minor effect of respiratory illness (without fever)
on breast milk intakes.26,27
Our regression analysis failed to find any association with upper
respiratory tract infections and milk intake; it is not clear whether
this was because our variable was an insensitive marker of illness.
BFP
mothers may perceive feeding difficulties and attempt to increase milk
intake by breastfeeding more frequently or by using more nonbreast milk
liquids. Given the documented high frequency of feeding events, it seems
more likely that mothers would introduce other liquids to supplement a
perceived inadequate milk supply than increase the number of feeds. In
this study, there was an increased total use of teas, but not bovine
milk, among the BFP infants that would support this explanation.
There are cultural taboos against breastfeeding during pregnancy throughout the world.1–5 Despite this, the practice is common.7,8,28,29
In Bangladesh, an estimated 20% of women who were lactating and
pregnant were still lactating at the beginning of the ninth month.28 In Guatemala, 50% of pregnant women were breastfeeding an older children.7,8
In Peru, 10% of women with preschoolers continued to breastfeed until
the last trimester of pregnancy (G.S.M., unpublished data). Similar
prevalence data for US women are not available, but the breastfeeding
behavior is present.3–5
Before health professionals can offer appropriate advice to women, the
biological consequences of the breastfeeding behavior need to be
understood.
Few researchers have looked at the consequences of a lactation-pregnancy overlap. Merchant et al7,8
reported that an overlap was associated with a non-significant decrease
of 57 g in birth weight; the effect increased with the overlap
duration. Studies with the appropriate design to look at birth outcomes
(risk of low birth weight or prematurity) have not been conducted yet. A
longer cohort study is needed to determine the cumulative effect of an
overlap on exclusive breastfeeding and infant health and growth through 6
months, as well as its effect on the mother and toddler. If future
studies confirm a negative effect of an overlap, then consideration
needs to be given to the optimal time to wean during pregnancy. However,
if additional studies find that infants and mothers adjust their
feeding behavior and are able to exclusively breastfeed for 6 months
with adequate growth, there is no reason to wean a toddler before a
mother wishes to do so. With these additional results, health
professionals will be able to provide advice that will lead to optimal
health for the infant, toddler, and mother.
Acknowledgments
This work was funded by National Institutes of Health R03 grant HD35183–03.
We
thank the field staff of the Instituto de Investigación Nutricional for
their outstanding work; the staff at the Instituto Materno Perinatal,
the Hospital Materno-infantil, Huascar, and the Ministry of Health
facilities in San Juan de Lurigancho in the study community for
facilitating access to mothers who gave birth in their units; and the
Iowa State University Community Nutrition Research group for their
critical review of the manuscript.
Comments
Post a Comment