The Effect of Serum β-Human Chorionic Gonadotropin on Pregnancy Complications and Adverse Pregnancy Outcomes: A Systematic Review and Meta-Analysis

Table 2

Literature risk of bias assessment.

Study	Selection				Comparability control for important factor	Exposure			NOS
	Adequate definition of case	Representativeness of the case	Selection of controls	Definition of controls		Ascertainment of exposure	Same method of ascertain for cases and controls	Nonresponse rate
Brajenović-Milić		—	—		—			—	4
Cai						—			7
Ding		—			—				6
Gonen		—			—	—			5
Han (1)						—			7
Han (2)		^—			—				7
Lepage					—				7
Li		—				—		—	5
Onderoğlu		—			—			—	5
Sharony					—	—			6
Sirikunalai		—							7
Yaron		—			—	—			5
Zeng						—			7