Kids guts and all part 2

The gut microbiome is highly unstable during the first two to three years of life¹. The intestinal microbiome of most infants resembles that of their mother; however, after one year of age, a complex and distinct microbiome profile develops². Children younger than three years of age have significantly lower diversity compared to adults. The bacterial communities evolve towards an adult-like configuration within the three³– or four-year⁴ period after birth. However, some studies suggest the gut microbiota is not yet established at five years of age⁵.

The most important bacterial colonisation of the gut occurs at the time of birth, when infants born via natural delivery are inoculated with a complex mixture of maternal vaginal micro-organisms⁶ that babies may not receive when delivered via Caesarean section⁷. Infants born by Cesarean section are initially colonised by bacteria from the environment, such as from maternal skin and hospital staff⁸ . Lactobacillus is highly abundant in the maternal vagina⁹ and infants born through the mother’s birth canal contain relatively high levels of Lactobacillus as part of their microbiome profile, while infants born by C-section do not. In one study, low levels of Lactobacilli persisted for the first six months after birth and up to three years of age¹⁰.

During the first few weeks, the microbiota of the newborn gut resembles the maternal skin and vaginal microbiome. In fact, the research shows how similar the infant gut microbiota is to the mother’s vaginal or skin microbiota, depending on the mode of birth¹¹. Pre-term infants exhibit different microbiome colonisation patterns when compared to full-term infants, and the hospital room environments contribute to infant microbiome development. Some strains detected in hospitalised infants also occur in sinks and on surfaces in the hospitals and belong to species often implicated in infection¹².

C-section is a lifesaving practice that is needed in 10% to 15% of births to avoid risking the life of mother or child¹³. However, C-section delivery is often overused, and in some regions of the world reaches 43% of births¹⁴. C-section circumvents natural exposure to the vaginal microbiota during labor and birth and, in addition, involves preventive antibiotics, which have also been related to dysbiosis. Cesarean delivery alters the bacterial colonisation of the gut¹⁵ for more than six months¹⁶. Cesarean born infants harbored less Bifidobacterium and Bacteroides species compared to children born naturally¹⁷ and the gut microbiota of infants, even at 24 months of age, is less diverse than those delivered naturally¹⁸.

The problem with this is that evidence now supports a direct association between early microbiota impact—including C-section—and obesity, with a related increase in being severely overweight at six weeks of age, an 83% greater risk of being obese¹⁹ or overweight by age 11²⁰ and obesity later in life²¹. Similar results of increased obesity are seen in animal studies²². As well, C-sections are closely linked with increases in immune-related diseases such as type 1 diabetes²³, allergies²⁴, and celiac disease²⁵ and inflammatory bowel disease (IBD), regardless of parental history²⁶. A number of large studies have now shown that Cesarean delivery is associated with wheezing and allergic sensitisation²⁷. A meta-analysis of 23 studies found a 22% increased risk of asthma associated with Caesarean birth²⁸.

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2. Mackie et al., 1999; Palmer et al., 2007.
3. Yatsunenko et al., 2012.
4. Bergström et al., 2014.
5. Cheng et al., 2015.
6. Makino et al., 2014; Milani et al., 2015.
7. Mueller et al., 2015.
8. Biasucci et al., 2008.
9. Chu et al., 2017.
10. Nagpal et al., 2016.
11. Dominguez-Bello et al., 2010.
12. Brooks et al., 2017.
13. Hannah et al., 2000.
14. Betrán et al., 2014.
15. Rotimi et al., 1985; Gronlund et al.,1999; Debley, 2005.
16. Gronlund et al., 1999.
17. Adlerberth et al., 2006.
18. Jakobsson et al., 2014.
19. Martinez et al., 2017.
20. Blustein et al., 2013.
21. Huh et al., 2012; Mueller et al., 2016; Darmasseelane et al., 2014.
22. Cox et al., 2014.
23. Phillips et al., 2012.
24. Bager et al., 2008.
25. Decker et al., 2011.
26. Bager et al., 2012.
27. Negele et al., 2004; Debley, 2005.
28. Thavagnanam et al., 2008.