Mode of Delivery and the Effect on
Intestinal Bacteria
Erin Smith
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Table of Contents
Intro……………………………………………………………………...pg. 3
Background Information………………………………………..pg. 4
Case studies and analysis…………………………………….....pg.6
Conclusion……………………………………………………………..pg.13
Work Cited…………………………………………………………….pg. 14
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Intro:
In a country where there is an obesity epidemic, Americans are becoming more
concerned about their health and are trying to find ways to improve it. The business of
vitamins, supplements, and functional foods is a growing trend. A specific trend that has been
growing is probiotics, prebiotics, and trying to obtain and maintain a healthy micro-flora or
healthy “gut”. Probiotics are defined as ‘live micro-organisms which confer a health benefit on
the host when administered in adequate amounts’ (Ref ID 12). There are capsules of probiotics
to take as well as foods like yogurt and other fermentable products, where probiotics and
prebiotics are added. This business is also now expanding to products such as cookies and
candy. Some of the claims that many of these products have are: to decrease intestinal transit
time, they can boost your immunity, keep you looking beautiful and help you digest foods. To
make these claims the companies have to be approved or notify the FDA, depending on the
type of claim. (probiotics.org)
A growing concern is if the mode of delivery will affect an infant’s micro-flora and the
possible immediate impacts and lasting impact it can have throughout their life. The live
cultures perform a variety of activities that range from nutritive to metabolic and protective
functions. These affect both the intestinal physiology, and the whole-body metabolism and
immunity. (Ref ID 8) The question is does an infant gain the same amount of bacteria necessary
for that initial micro-flora development the same when born vaginally and by caesarean
section? This could pose more of a problem now than it did 20 years ago due to convenience
caesarean sections. Women want to avoid labor pain and like to be able to schedule delivery at
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a convenient time. ( womensnews.org) Is there enough research to tell the mother the cons of
cesarean delivery when it comes to the development of an infant’s micro-flora? The fetal
intestine is sterile and during birth it’s bathed in and swallows amniotic fluid (ref ID 6). The
maternal intestinal flora is a source of bacteria for the neonatal gut and this is where it is
thought to be the first “main” introduction of bacteria to the intestines.(ref ID 6) Without going
through the birth canal the question arises if the infant is going to obtain the same type and
amount of bacteria that it needs to ensure a healthy gut.
Most studies have shown that there is a delay in fecal colonization with those that are
born by caesarean section. This could result in GI distress as well as a compromised immune
function. Another possible impact on the fecal colonization is whether the child is breast-fed or
formula-fed. According to many studies, environmental factors may be more important than
breastfeeding in gut colonization after delivery. Environmental factors are extremely important
for the intestinal colonization of infants born by caesarean section. (ref ID 6) Lastly, antibiotic
intake either through the mother before birth or the child after birth has shown to impact the
colonization in the intestines.
Background Information:
Many of the studies test the infant’s fecal matter to get an idea of the bacteria that was
colonizing in the infant’s colon. Some of the main bacteria that were mentioned or found are
Bifidobacterium. This is often added in probioitic supplementation and has been shown to
have beneficial effects in various pathologies, including allergic diseases, but its role in
immunity has so far been little known (Ref ID 11). This bacterium represents 90% of the total
gut micro-flora in breast-fed babies and up to 15% in adults.( Ref ID 11) This bacteria is what
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we want to be colonized at an early age and has been shown to be more prevalent in babies
born vaginally.
The other two bacteria that were mentioned the most throughout the research results
were E. coli and C. difficile. Many are already aware of E. coli and some of the possible side
effects that come along with it such as diarrhea, nausea, and stomach cramping. There has
been many recalls because of E. coli contamination in the US and this is why so many know
about this bacteria as opposed to the others. The other bacterium, C. difficile is being
increasingly implicated as the leading cause of diarrhea and colitis. (ref ID 13) C. difficile is often
a major enteric pathogen responsible for antibiotic-associated diarrhea. During early infancy,
asymptomatic colonization by C. difficile is common and the intestinal microbiota shows low
complexity. (ref ID 14) These two bacteria are more prevalent in caesarean section births.
The methods that was most common when trying to determine the bacteria that were
present in the intestines is by using DGGE and temperature gradient gel electrophoresis (TGGE).
These are molecular fingerprinting techniques that are being used more frequently in microbial
ecology. When this is combined with the sequencing of 16S rDNA clones and this helps
determine the different bacteria that are present in this microbial community. These combined
help obtain profiles of the intestinal microbial community.(ref Id 15)
When an infant is born their gastrointestinal tract is sterile. During the birth of
the baby it becomes colonized with bacteria mainly from their mother. When a baby is
vaginally delivered it comes in contact with the vaginal and intestinal flora of the mother which
starts the colonization.(ref id 3) If the baby is born by cesarean section it does not come into
contact with the mothers flora so is relying exclusively on the environmental bacteria to aid in
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colonization.(ref ID 2) Some authors have suggested that the composition of the very first
human microbiota could have long-lasting effects, up to months or even years (ref ID 3)
Case studies and analysis:
In the study titled “Cesarean Delivery May Affect the Early Biodiversity of Intestinal
Bacteria” looks at the impact of the mode of delivery and the intestinal bacteria colonization.
They took forty-six full term infants that were born in October of 2003 from a hospital in Italy.
They obtained fecal samples on day three of life, before the infants were discharged from the
hospital. They then did the DGGE and TGGE to determine the different bacteria present. The
results from this study showed that Bifidobacterium was found in 13 of 23 samples derived
from the vaginally delivered newborns but was not found in any of the samples from the babies
born by cesarean section. They found 9 of 23 vaginally delivered babies had E. coli where only
2 of the 23 cesarean born babies tested positive. The results from the fecal samples of the
babies born vaginally had more variations where as the babies born by cesarean displayed
more constant profiles. There are not many studies done to know if the colonization of
bacteria within the first three days of life is dominant, but this study represents that a
newborn’s intestinal microbiota is strongly influenced within three days of life with little to no
influence of the type of feeding. This study had a relatively small group and they tried to
exclude different criteria to try and ensure that there was no variation in the study. (ref ID 3)
Unlike the last study this study titled “Factors Influencing the Composition of the
Intestinal Microbiota in Early Infancy” had a large research group. They took 1032 infants fecal
samples at one month of age. They recruited participants with diverse lifestyles, at 34 weeks of
gestation. Pregnant women with conventional lifestyles were recruited through another study
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that was on pregnancy related pelvic girdle pain and pregnant women with an alternative
lifestyle were recruited through organic food shops, anthroposophic (alternative medicine)
doctors and midwives. The subjects would receive a tube with a spoon, sanitary napkin, an
instruction form, and a brief questionnaire. The parents would then receive the sample at the
appropriate time and send the sample in as soon as possible. They would exclude samples if
there was an insufficient amount of feces. They also excluded feces collected before the age of
three weeks and after the age of six weeks. Since they had the questionnaire they tried to take
into account other characteristics such as the child’s health, as well as hygiene, infections,
nutrition, child rearing, and other lifestyle characteristics. More than half of the infants were
born in the hospital and approximately 10% of all infants were born by cesarean section. With
the vaginal delivery at home compared to the cesarean section, the cesarean section resulted in
lower colonization rates and counts of bifidiobacteria and B fragilis-group species, whereas the
prevalence counts of C difficile and E coli were higher. The biggest difference was the vaginal
delivery babies were 100 fold lower in the amount of C difficile, and 100 fold higher respectively
for the cesarean section babies. Below is the prevalence percent of different bacteria and
mode of delivery that was determined in this study. (ref ID 4)
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Bifidobacteria
Place and
Prevalence %
mode of
delivery
-Natural
99
delivery at
home
-Natural
99
delivery in
hospital
-Artificial
100
delivery in a
hospital
-Cesarean
96
section in
hospital
E coli
C difficile
Prevalence
%
B fragilisGroup
Prevalence
%
Prevalence
%
Lactobacilli
Prevalence
%
85
19
83
32
91
26
85
34
91
34
87
30
88
42
63
32
Most of the babies were breastfed exclusively up to the first month of life, where as 232
infants were formula fed exclusively and 98 infants received a combination of breastfeeding
and formula feeding. The infants that were formula fed exclusively were more often colonized
with E coli, C difficile, B fragilis group, and lactobacilli then were their exclusively formula-fed
counterparts. (ref. ID 4) When looking at these studies if the type of nutrition is not specified
than it could skew the data. The first study discussed that the type of feeding had very minimal
impact on the development of microflora, but this was only in the first three days of life. This
study suggests that within the first month of life the type of nutrition has an impact on the
intestinal development.
A study that was published in the Journal of Pediatric Gastroenterology and Nutrition
took a look at the “Microbiota of 6-week-old infants Across Europe: Geographic Influence
Beyond Delivery Mode, Breast-feeding, and Antibiotics”. This study was done with 606 infants
from 5 European countries with different lifestyle characteristics. Mothers of newborn infants
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filled in first questionnaire recording events concerning pregnancy and delivery. Once the baby
was 6 weeks old, mothers filled in a second questionnaire concerning feeding method, health
history of the baby at approximately 6 weeks, antibiotic treatment of infants or breast-feeding
mother, and so forth. At the age of six weeks, the infants’ parents would provide a fecal
sample. Some would call the lab and they would go pick it up still in the diaper. Others would
take the sample and deliver it under anaerobic conditions quickly to the laboratory, or the
infant provided the sample at the clinic. They would try to get the sample within four hours
under anaerobic conditions at 4 degrees Celsius regardless of how they received the sample
before they would analyze it. This was done to try and cut down on variability. (ref ID 7)
The results of this study, like the previous studies, showed that the mode of delivery
does have an impact on some bacterial groups. Compared with the cesarean section, vaginal
delivery was associated with higher average proportions of Bacteroides, and lower proportions
of the C. coccoides group. The table below shows the results and how you can compare.
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The white represents babies born vaginally and the black are the babies born by cesarean
section. The vaginally delivered babies showed an overall higher number of detected groups
compared with other babies. (ref ID 7)
The results also found differences in the bacterial groups detected with the different
feeding methods (fully breast-fed, formula feeding, and mixed feeding). They found that
breast-fed infants had significantly greater proportions of bifidobacteria and significantly lower
proportions of bacteroides, C coccoides, and Lactobacillus groups compared with formula-fed
babies. The breast-fed babies also presented lower proportions of Bacteroides compared with
mixed-fed babies. The mixed-fed babies did have a higher proportion of bifidobacteria than the
formula-fed. Below is a graph that represents this data that was collected.(ref ID 7)
The white represents breast-fed infants, the black is formula fed infants, and the striped is
mixed.
This study shows that the mode of delivery and the type of feeding that is used does
have an impact on the development of gut microbiota. They looked at several other important
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variables that could have an impact on the microbiota such as the lifestyle. It is very important
when looking at these results to keep in mind that they do have different lifestyles which will
have an impact on the results. It also is good because not every baby is raised the same way
and on the same food so it puts it in real life perspective.(ref ID 7) Another thing to keep in
mind when looking at these last three studies is that they all took samples from the parents.
This could cause a difference in the results because it is hard to ensure that they would get the
samples in the same amount of time. It leaves room for discrepancy.
According to Nutrition Research Reviews article called “Breast-v. Formula-feeding:
impacts on the digestive tract and immediate and long-term health effects”; breast-feeding is
associated with lower incidence of necrotizing entercolitis and diarrhea during the earlier
period of life and with lower incidence of inflammatory bowel diseases, type 2 diabetes and
obesity later in life. Breast milk is beneficial for infants because the complex composition of
human milk changes over the lactation period modifying to the infants needs at the time of
growth. (ref Id 8) In addition to the nutrients, human milk also contains hormones, growth
factors, immunoglobulins, cytokines, enzymes, ect that support both the growth and the
passive defences of the infant (ref id 8) Does the type of feeding impact the microbial
development in infants? The first study that was discussed found that there were little to no
influence of the type of feeding. These results were only taking into account the first three
days of life.(ref ID 3) The second study suggests that within the first month of life the type of
nutrition has an impact on the intestinal development, (ref ID 4) and the third study that was
done throughout Europe found that the type of feeding that is used also has an impact on the
development of gut microbiota (ref ID 7). Two out of the three studies that were mentioned
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felt that they had enough information and data to say that the type of feeding has an overall
effect on the intestinal bacteria development.
The study titled “Molecular Monitoring of Succession of Bacterial Communities in
Human Neonates” that was published in Applied and Environmental Microbiology did a study
that shows whether the type of feeding has an impact on the micro-flora. This study used two
healthy full term baby boys with the consent of their parents. They were both vaginally
delivered and breast-fed immediately after birth. One of the babies received breast milk
completely until weaning period, which was at 130 days. Infant formula was then added to the
diet starting on day 150 and gradually replaced breast feeding, until day 200 when it was
completely withdrawn. The other infant was breast fed until day 17, when he received the first
formula food, and then the proportion of formula milk was progressively increased with time;
solid food was given after 3 months. Fresh fecal samples were taken daily during the first two
weeks of their life and then twice a month for 10 to 12 months. (ref ID 15)
The baby that was breastfed until day 200 showed that as soon as he started getting
weaned his bacterial profile remained unstable. Just after the end of breast feeding, which was
on day 198, the bacteria bifidobacteria disappeared momentarily and the intensity of this
bacterium never recovered in the period from 7 to 10 months. On day 200 the more diverse
bacteria began to appear and started to become stronger. The other infant that was breast fed
until day 17, and then an increasing quantity of formula milk was added to his diet showed a
little different results. As breast feeding was gradually replaced by formula milk, the profiles
became more complex, and bands corresponding to other bacteria distantly related to
uncultured bacteria became more dominant. This pattern continued when solid food was
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introduced into the infant diet during month 4. There were very low amounts of Enterococcus
and the Bacteroides. From 4 to 6 months the profile remained quite stable despite the
introduction of solid food and from 6 to 9 months there were some more pronounced shifts in
the profiles. After 9 months the profiles stabilized again until monitoring was stopped after 1
year. Both of the babies had similar features. They both had colonization by bifidobacterial
species, which were detected on the third or fourth day of life. Bifidobacteria was most
dominant in breast-fed baby during the first six months of life. The baby that was fed both
human and formula milk had the amplicons which is related to bifidobacteria and is less
intense. This study showed that there is an impact on the type of feeding and the development
of micro-flora. The baby that was breast-fed had more of the “healthy” Bifidobacteria that aids
in digestion and is competitive to potential harmful bacteria. (ref Id 15)
Conclusion:
The mode of delivery and the type of feeding has data supporting that it does effect the
development of an infant’s intestinal micro-flora. Many of the studies show that the infants
born vaginally provide and encourage the growth of the Bifidobacteria, and the infants born by
cesarean section have evidence of more E. coli and C. difficile. Studies have shown that it can
take anywhere from months to years for the micro-flora of an infant born cesarean to get to
the same progress of an infant born vaginally.(ref ID 3) Some studies should be done where the
feces samples are all taken at a clinic or location of the studies and they also need to ensure
that the same infant formula is used with all infants if at all possible. This would cut down on
the inconsistency.
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Works Cited
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