Table 1. Characteristics of studies in the meta-analysis.

Author	Year	Country	Study design	Follow up	SUA	TVC
Gornall [15]	2003	UK	Cohort retrospective	1995–2001	107	214
Predanic [21]	2005	USA	Case control	1999–2004	84	84
Bombrys [14]	2008	USA	Cohort retrospective	2000–2006	255	289
Horton [16]	2010	USA	Case control	2000–2008	68	68
Hua [17]	2010	USA	Cohort retrospective	1990–2007	392	63,655
Khalil [18]	2013	Saudi Arabia	Cohort retrospective	2004–2012	159	35,026
Mailath-Pokorny [19]	2015	Austria	Cohort retrospective	2004–2011	136	500
Ashwal [12]	2014	Israel	Case control	2008–2012	91	182
Battarbee [13]	2015	USA	Cohort retrospective	2007–2014	219	219
Naveiro-Fuentes [20]	2016	Spain	Cohort retrospective	2007–2014	127	27,752
Tülek [11]	2015	Turkey	Cohort retrospective	2006–2013	93	100

Only first author of each study is given.

SUA, single umbilical artery; TVC, three vessel cord.