Gastrointestinal consequences of cesarean section birth: A systematic review of short- and long-term effects in infancy and beyond

Table 9 Summary of included studies on gut microbiota differences by delivery mode

Ref.	Country/population	Key findings	Persistence of difference	Modifiable factors examined	Risk of bias
Nagpal et al[27], 2017	Japan/Healthy full-term infants	VD enriched with Lactobacillus, Bacteroides; C-section infants had reduced colonization	Seen up to 3-6 months	Not specified	Moderate (small sample, unclear confounder control)
Kim et al[25], 2021	Korea/National cohort	C-section associated with lower Bifidobacteria, delayed microbiota maturation	Persisted into infancy (12 months)	Breastfeeding	Low (large cohort, confounders adjusted)
Reyman et al[28], 2019	Netherlands/n = 117	C-section infants had low species richness, delayed Bacteroides	Up to 6 months	Antibiotics, feeding method	Moderate (small sample, well-defined methods)
Shao et al[24], 2019	United Kingdom/Baby Biome Study	C-section disrupted maternal strain transmission; ↑ Klebsiella, Enterococcus	Persistent at 1 year	Antibiotics, feeding, maternal FMT	Low (large, multicenter, robust metagenomics)
Mitchell et al[29], 2020	United States/Israel/Multiethnic cohort	Bacteroides absent in C-section infants for weeks; antibiotic-sensitive	6-12 weeks	Antibiotics, breastfeeding	Moderate (multi-site, antibiotic exposure varied)
Bäckhed et al[26], 2015	Sweden/n = 98	VD infants dominated by Bifidobacterium, Bacteroides; C-section → ↑ Clostridium	Up to 3-4 months	Breastfeeding	Moderate (well-designed but small sample)
Dos Santos et al[33], 2023	Canada/National cohort	C-section disrupted diversity; ↑ Proteobacteria in early life	Up to 12 months	Hospital stay, feeding type	Low (population-wide registry, controlled)
Dominguez-Bello et al[34], 2010	United States/Pilot cohort	VD infants resembled vaginal flora; C-section resembled skin/hospital flora	Neonatal period	FMT, vaginal seeding	High (pilot study, small sample, proof-of-concept only)

C-section: Cesarean section; FMT: Fecal microbiota transplant; VD: Vaginal delivery.