Examining the relationship between maternal body size, gestational glucose tolerance status, mode of delivery and ethnicity on human milk microbiota at three months post-partum

Table 2 Associations between maternal characteristics and top 5 phyla and top 10 genera: Grouped by BMI

Taxa	Group effect p-value	Pairwise comparison	IRR	95% CI	Pairwise comparison p-value
Pre-pregnancy BMI
Phylum
Proteobacteria	0.019	Obese vs overweight	0.62	0.43–0.90	0.012
Proteobacteria	0.019	Overweight vs healthy	1.23	1.00–1.50	0.045
Bacteroidetes	0.0051	Obese vs overweight	3.70	1.61–8.48	0.002
Bacteroidetes	0.0051	Obese vs healthy	2.56	1.27–5.17	0.0086
Genus
Staphylococcus	0.011	Obese vs overweight	2.50	1.09–5.72	0.031
Staphylococcus	0.011	Obese vs healthy	3.15	1.47–6.76	0.0032
Corynebacterium	0.0003	Obese vs overweight	5.13	1.79–14.70	0.0023
Corynebacterium	0.0003	Obese vs healthy	4.98	2.11–11.74	0.0002
Brevundimonas	< 0.0001	Overweight vs healthy	8.72	3.24–23.48	< 0.0001
	< 0.0001	Unscheduled C-section vs vaginal	16.70	5.99–46.57	< 0.0001
	< 0.0001	Scheduled C-section vs unscheduled C-section	0.071	0.011–0.46	0.0053
3-month post-partum BMI
Phylum
Actinobacteria	0.0058	Obese vs overweight	2.34	1.38–3.98	0.0017
Actinobacteria	0.0058	Obese vs healthy	2.02	1.18–3.46	0.010
Genus
Corynebacterium	< 0.0001	Obese vs overweight	4.84	2.19–10.72	0.0001
Corynebacterium	< 0.0001	Obese vs healthy	7.77	2.95–20.43	< 0.0001
Brevundimonas	0.0005	Obese vs overweight	8.89	2.29–34.57	0.016
	0.0005	Obese vs healthy	9.56	2.17–42.22	0.0029
	< 0.0001	Unscheduled C-section vs vaginal	13.01	4.01–42.20	< 0.0001
	< 0.0001	Scheduled C-section vs unscheduled C-section	0.08	0.013–0.62	0.015

Separate Poisson regression models were run for pre-pregnancy BMI and 3-month post-partum BMI, while adjusting for maternal glucose tolerance status, mode of delivery, DNA extraction batch, and PCR sequencing batch. Statistically significant main group effect findings shown only (group effect: p ≤ 0.022 for phylum, p ≤ 0.017 for genus; pairwise comparison: p < 0.05). An interaction term between pre-pregnancy BMI and maternal glucose tolerance status was found to be statistically significant for Gemella. No other statistically significant interactions were found between maternal pre-pregnancy BMI and glucose tolerance status. Gemella showed an increased incidence among mothers with an overweight BMI (versus healthy BMI) and concurrent gestational diabetes IRR, CI (5.96 [1.85–19.21], p = 0.0028). An increased incidence of Gemella was also observed in mothers with an obese BMI and concurrent impaired glucose tolerance versus both mothers with overweight (11.42 [1.49–87.67], p = 0.019) and healthy weight BMIs (4.04 [1.63–10.01], p = 0.0026). Abbreviations: confidence interval CI, incidence rate ratio, IRR

ISSN: 1471-2180