Table 1.

Characteristics of studies included in this meta-analysis.

First authorreference	Year of publication	Country (region)	Ethnicity	Study design	Number of cases	Controls	Matching criteria	Genotyping method	MAF in controls
Beltcheva25	2014	Bulgaria (Sofia)	European	Case-control	130	130	Age and degree of obesity	TaqMan	0.10
Han26	2015	China (Nantong)	Asian	Cross-section	128	140	–	PCR-RFLP	0.26
Hua27	2014	China (Wuxi)	Asian	Case-control	112	150	Age and gestational week	PCR-RFLP	0.49
Li28	2013	China (Beijing)	Asian	Case-control	264	172	–	Sequencing	0.24
Liu29	2006	China (Wuxi)	Asian	Case-control	52	34	Age and gestational week	PCR-RFLP	0.47
Low30	2011	Malaysia (Selangor)	Asian	Case-control	26	53	–	PCR-RFLP	0.18
Takhshid31	2015	Iran (Shiraz)	Asian	Case-control	65	70	Age	PCR-RFLP	0.11
Zhang32	2014	China (Nanning)	Asian	Case-control	98	135	Age, BMI and gestational week	PCR-RFLP	0.27

MAF: minor allele frequency; PCR-RFLP: polymerase chain reaction-restriction fragment length polymorphism; BMI: body mass index.