Answer by Tirumalai Kamala:
I see this as a two-part question.
- Why does birth delivery mode matter for baby’s immune function?
- Is the microbiota of a water-birth vaginal delivery likely to be different from that of a normal-birth vaginal delivery?
Let’s examine them in sequence.
1. Why does birth delivery mode matter for baby’s immune function?
Having grown in mother’s quasi-sterile* uterus, we acquire our final tissue post-birth. This tissue is our microbiota, which colonizes various parts of our body (oral, gastrointestinal [GI], nasopharyngeal, respiratory and reproductive mucosae, and skin), and transforms each one of us profoundly and permanently from an individual into a multitude.
How does this process work? Taking a leaf out of’s “small world” concept, Baquero and Nombela (1) propose that a microbial “six degrees of separation” principle applies to the process of post-birth microbial colonization. According to this idea, we get seeded immediately post-birth by bacterial “pioneer” (starter) species such as Lactobacillus, Prevotella or Sneathia during vaginal birth (2, 3). These pioneer populations are then reinforced and embellished by additional microbial partners through breast feeding. These early colonizers serve as “sinks or attractors for other microbial partners”, and the ensuing “consortia of organisms in turn create novel niches for other organisms”.
In recent years, a tremendous variety of data suggests that early life acquisition of our microbiota influences our long-term health for better or worse. In the natural mode, i.e. vaginal delivery, we get colonized by aerobic or facultative anaerobic bacteria like Enterobacteriaand Enterococci. Oxygen-dependent/preferring, these bacteria proceed to change the neonatal gut milieu, making it amenable for anaerobic bacteria such as Bifidobacteria and Bacteroides. Over time, aerobes and facultative anaerobes decline and anaerobes prevail in our gut (4, 5).
Early-life sequence and degree of microbial colonization matters for our long-term health since perturbations in either are associated with diseases such as allergy, asthma, atopy among many others. Thus, birth delivery mode is crucial in the context of the initial sequence of microbial colonization. Vaginal? We first acquire microbes from the birth canal. Caesarean-section (C-section)? We first acquire microbes from the delivery area and mother’s skin.
Immediate post-birth Vaginal and Caesarean-section (C-section) birth infant differences
- Vaginally-delivered newborns acquire their mother’s GI and vaginal microbiota (Bacteroides, Bifidobacteria and E.coli) as they pass through the birth canal (6, 7, 8). C-section-delivered infants lack such bacteria.
- As long ago as 1987, Bennet and Nord in Sweden (9) reported that E. coli and enterocci appear in newborn stool within 24 hours of birth while anaerobic Bacteroides and Bifidobacteria appear within two days post-birth. On the other hand, C-section-delivered infants had lower Bacteroides and Bifidobacteria, and higher Klebsiella.
- Stool sample cultures from 116 Swedish infants (99 vaginal births, 17 C-section ) born between 1998 and 2000 showed C-section-delivered children had reduced gastrointestinal (GI) colonization by Bacteroides and E. coli in the first 6 to 12 months of life (10).
- Stool sample cultures from 300 British, Italian and Swedish infants examined from birth to 12 months of age showed that at one year of age, C-section-delivered infants had lower ratio of anaerobic to facultative bacteria compared to vaginally-delivered infants (11).
- Stool sample cultures from 64 Finnish infants (34 vaginal births, 30 C-section) born between 1995 and 1996 showed much lower Bacteroides fragilis colonization in C-section-delivered infants, ranging from not at all at 2 months of age to half that of vaginal births at 6 months of age. On the other hand, C-section-delivered infants had more than 3 fold higher levels of Clostridium perfringens at 1 month of age (12). Higher neonatal GI tract loads of this bacterium is associated with “flatulence, distended abdomen, foul-smelling stools, diarrhea, and blood in stools” (13).
- C-section delivered infants have expanded Enterobacteriaceae other than E. coli such as Klebsiella and Enterobacter, and clostridia including C. difficile (7, 10, 11). Higher Clostridium counts are associated with higher clinical complications and hospital admissions (7).
- Vaginally-delivered infants harbor a greater variety of bacteria (79 species/species clusters) compared to C-section deliveries (54 species/species clusters) (14).
- C-section deliveries have lower proportion of Bacteriodes and Atopobium (15).
- C-section deliveries also have lower proportion of Bifidobacteria (16)
- Using 16S rRNA sequencing, Dominguez-Bello et al (17) compared infant and mother bacterial communities on their skin (ventral forearms), oral mucosa, vagina (mother) and nasopharyngeal aspirate and rectal swab (infant). They took the infant samples within seconds of birth except the rectal swabs which they took 24 hours post-birth, and mothers’ samples 1 hour before birth. They made two observations.a) Regardless of mode of delivery, bacterial community composition was rather homogenous across the infant body (skin, and oral, nasopharyngeal and rectal mucosae) immediately post-birth.
b) Vaginally-delivered infants’ bacterial communities resembled those of their mothers’ vaginal communities (Lactobacillus, Prevotella, Atopobium, Sneathia species) while C-section-delivered infants’ bacterial communities resembled those of their mothers’ skin communities (Staphylococcus species).
From 18 using data from 17
Long-term post-birth Vaginal and Caesarean-section (C-section) birth infant differences
- C-section births have delayed establishment of stable microbiota (19).
- C-section births correlate with higher rates of asthma, celiac disease, obesity and Type 2 diabetes (20).
From 18 (data from 21, this study did not control for delivery method and had 5 out of 33 C-section deliveries in the probiotic group, and 11 out of 35 C-section deliveries in the placebo group).
- C-section delivery was associated with a statistically significant higher rate of wheezing and allergic sensitization to specific foods such as codfish, cow’s milk, egg, peanut, soybean, wheat (22).
- A database analysis for association between C-section delivery and food allergy/food atopy, inhalant atopy, eczema/atopic dermatitis, allergic rhinitis, asthma, and hospitalization for asthma in papers published from 1966 to May 2007 suggested a moderate risk increase for allergic rhinitis, asthma, hospitalization for asthma, and perhaps food allergy/food atopy, but not with inhalant atopy or atopic dermatitis (23).
Thus, exposure to mother’s vaginal microbiome is important for proper conditioning and functioning of the infant’s immune system. Studies suggest C-section children develop higher rates of asthma and allergy later in life.
2. Is the microbiota of a water-birth vaginal delivery likely to be different from that of a normal-birth vaginal delivery?
I could not find a peer-reviewed study that directly compared microbial colonization between normal- and water-birth vaginal delivery. However, there are two pieces of published data that suggest they could be different.
- Penders et al (7) show that vaginally-delivered infants born in a hospital have more Clostridium difficile in their GI microbiota compared to those born at home. van Nimwegen et al (24) also compared vaginal home versus hospital delivery. They monitored stool sample cultures at 1 month of age and measured the blood anti-food antigen IgE of the infants at ages of 1, 2 and 6 to 7 years. They too found higher C. difficile colonization with vaginal hospital delivery and further found it to be associated with an increased risk of asthma, eczema, food sensitization and wheeze.
- As Spor et al show (25), immediate post-birth colonization is unstable. In fact, stable microbial colonization doesn’t set in until adulthood.
I thus speculate that with water-birth vaginal delivery, early microbial colonization may start out similar to normal-vaginal delivery but could get more easily diluted and/or washed out. Consequently, your child’s early microbiota was likely a hybrid of vaginal- and skin-associated. Is that bad for your child’s immune function? Only time will tell. As Spor et al’s figure shows, delivery mode is only one of several factors that sculpt early-life immune function, genetics and breast milk versus formula being the other important ones.
* We long thought that we develop in a sterile environment in the uterus and only get exposed to microbes post-birth. A recent study (26) published in the journal Science Translational Medicine shows that human placenta is stably colonized by a specific set of micro-organisms that most closely resemble those in maternal vagina/GI tract. Thus, it’s possible that at the very least, even in utero, babies may be directly exposed to microbial products, if not to microbes themselves.
- Bennel, R., and C. E. Nord. “Development of the faecal anaerobic microflora after caesarean section and treatment with antibiotics in newborn infants.” Infection 15.5 (1987): 332-336.
- Adlerberth, Ingegerd, et al. “Gut microbiota and development of atopic eczema in 3 European birth cohorts.” Journal of allergy and clinical immunology 120.2 (2007): 343-350.
- Grölund, Minna-Maija, et al. “Fecal microflora in healthy infants born by different methods of delivery: permanent changes in intestinal flora after cesarean delivery.” Journal of pediatric gastroenterology and nutrition 28.1 (1999): 19-25.
- Ahtonen, P., et al. “Clostridium perfringens in stool, intraparturn antibiotics and gastrointestinal signs in a neonatal intensive care unit.” Acta Paediatrica 83.4 (1994): 389-390.
- Fallani, Matteo, et al. “Intestinal microbiota of 6-week-old infants across Europe: geographic influence beyond delivery mode, breast-feeding, and antibiotics.” Journal of pediatric gastroenterology and nutrition 51.1 (2010): 77-84.
- Reid, Gregor, et al. “Microbiota restoration: natural and supplemented recovery of human microbial communities.” Nature Reviews Microbiology 9.1 (2010): 27-38.
- Hyde, Matthew James, and Neena Modi. “The long-term effects of birth by caesarean section: the case for a randomised controlled trial.” Early human development 88.12 (2012): 943-949.
- Negele, Kathrin, et al. “Mode of delivery and development of atopic disease during the first 2 years of life.” Pediatric allergy and immunology 15.1 (2004): 48-54.
- van Nimwegen, Frederika A., et al. “Mode and place of delivery, gastrointestinal microbiota, and their influence on asthma and atopy.” Journal of Allergy and Clinical Immunology 128.5 (2011): 948-955.
- Aagaard, Kjersti, et al. “The placenta harbors a unique microbiome.” Science translational medicine 6.237 (2014): 237ra65-237ra65.