Table 3.

Characteristics of all selected studies included on MTHFR joint mutations.

				Case No.		Control No.
Author	Provence	Publication year	Pregnancy loss(times)	Joint mutation	No mutation	Joint mutation	No mutation	HWE ∗	P value †	NOS score ‡
Wang et al, [23]	Shanghai	2006	≥2	23	27	7	28	Y	.61	8
Zhang et al, [56]	Zhejiang	2017	≥2	12	6	2	1	Y	.18	7
Zhu et al, [59]	Beijing	2018	≥2	48	88	23	28	Y	.32	9
Xu et al, [66]	Zhejiang	2019	≥2	41	4	28	18	Y	.72	9
Xu et al, [68]	Henan	2020	≥2	49	4	28	18	Y	.72	9