Table 1. The characteristics of eligible studies included in the meta-analysis.

Anthor(year)	Country	Geographical location	Population of cases	Source of control	Subjects	Sample size		P of HWE
						Case	Control	677	1298
Kumari et al. (2013)	India	Western/Central Asia	Cases having family history of any congenital malformation, kidney-related diseases and other severe diseases were excluded. Mean age was 5 years.	Mixed	Children	467	469	0.518	0.134
Aida et al. (2012)	Turkey	Western/Central Asia	Cases were excluded due to alternative diagnosis of their existing syndromic conditions. Age range not stated.	Mixed	Children	56	76/93a	0.105/0.779	0.187
					Mothers	54	76/93
Wang et al. (2012)	China	Eastern Asia	Not stated.	HB	Mothers	89	64	0.070
Han et al. (2011)	China	Eastern Asia	Cases with recognized congenital anomalies or syndromes were excluded. Mean age was 9.57±0.72 years.	HB	Children	187	213	0.236	0.545
Guo et al. (2009)	China	Eastern Asia	Cases having family history of any congenital malformation were excluded. Mean age was 9.04 years.	HB	Children	97	104	0.277
					Mothers	97	104
Ali et al. (2009)	India	Western/Central Asia	Syndromic patients as well as families with a syndromic member other than NSCL/P probands were not included. Age range for patients 4 months-24 years, for mothers 19–45 years.	PB	Children	323	214	0.916	0.395
					Mothers	116	214
Wan et al. (2006)	China	Eastern Asia	Cases having family history of any congenital malformation were excluded. Age range not stated.	HB	Children	48	60	0.075	0.210
Shotelersuk et al. (2003)	Thailand	Eastern Asia	All syndromic cases were excluded. Age range not stated.	PB	Children	109	202	0.478	0.876
					Mothers	67	202

HWE Hardy-Weinberg equilibrium; HB hospital based; PB population based.

^atwo groups of control.