Vitamin B12 status and folic acid/vitamin B12 related to the risk of gestational diabetes mellitus in pregnancy: a systematic review and meta-analysis of observational studies

Table 1 Characteristics of studies investigating the association between vitamin B12 and gestational diabetes mellitus (N = 10, from 2007–2022)

Study	Country	Study design	Sample size	Trimester of Vitamin B12	GDM diagnosis	Vitamin B12 and GDM			Folic acid/Vitamin B12 and GDM			Score
Study	Country	Study design	Sample size	Trimester of Vitamin B12	GDM diagnosis	OR	95%CI	P-value	OR	95%CI	P-value	Score
Wang, 2020 [23]	China	case–control	NR¹	Third trimester	IADPSGC²	1.31	1.03–1.68	0.03	-	-	-	4
Sukumar, 2016 [22]	British	Retrospective case–control	344	Second trimester	WHO 1999³	2.59	1.35–4.98	0.004	-	-	-	7
Krishnaveni, 2009 [17]	India	Prospective cohort-study	785	Third trimester	WHO 1999³	2.00	1.1–3.6	0.02	-	-	-	7
Chen, 2021 [25]	China	Prospective cohort-study	1058	First trimester	IADPSGC²	1.54	1.41–1.68	0.002	0.98	0.97–0.99	0.009	7
Li, 2019 [26]	China	Cross-sectional	406	Third trimester	IADPSGC²	0.30	0.15–0.60	< 0.05	3.08	1.63–5.83	< 0.005	7
Lai, 2018 [18]	China, India, Malaysia	Cross-sectional	913	Second trimester	WHO 1999³	0.81	0.68–0.97	0.02	1.97	1.05–3.68	0.034	7
Tan, 2020 [36]	Australia	Nested-cohort	325	Second trimester	WHO 2016⁴	0.99	0.83–1.18	0.913	1.37	0.71–2.62	0.347	7
Sukumar, 2021 [24]	British	Prospective cohort-study	4746	First trimester	IADPSGC²	0.86	0.79–0.93	< 0.05	1.74	1.23–2.44	0.003	7
Sukumar, 2021 [24]	British	Prospective cohort-study	4746	First trimester	IADPSGC²	1.20	1.00–1.44	0.05	1.74	1.23–2.44	0.003	7
Krishnaveni, 2007 [35]	India	Prospective cohort-study	654	Third trimester	Carpenter-Coustan criteria⁵	1.90	0.98–3.68	0.057	4.8	1.45–15.84	0.01	4
Li, 2022 [27]	China	case–control	1364	Second trimester	IADPSGC²	0.80	0.65–0.98	0.033		-	-	7

¹NR, Not Report
²IADPSGC, International Association of Diabetes and Pregnancy Study Groups (75 g OGTT, fasing > 5.1 mmol/L, 1-h > 10.0 mmol/L, 2-h > 8.5 mmol/L)
³WHO 1999, 1999 World Health Organization standard criteria (75 g OGTT, fasting > 7.0 mmol/L; 2-h > 7.8 mmol/L)
⁴WHO 2016, the new (2016) World Health Organization classification (fasting ≥ 5.1 mmol/L 2-h level of ≥ 8.5 mmol/L)
⁵Carpenter-Coustan (50 g OGTT, fasting > 5 mmol/L, 1-h > 10.0 mmol/L, 2 -h > 8.6 mmol/L, 3 -h > 7.7 mmol/L)

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