Table 2.

Quality assessment of included studies

Author	Year	Selection	Comparability	Exposure	Total
Tulinius	1992	★★★	★★	★★	7
Goldgar	1994	★★★	★★	★★	7
Hayes	1995	★★★	★★	★★	7
Isaacs	1995	★★	★★	★★	6
McCAHY	1996	★★	★	★★★	6
Glover	1998	★★	★★	★★	6
Rodriguez	1998	★★★	★★	★★★	8
Kalish	2000	★★★	★★	★★	7
Bai	2005	★★	★★	★★	6
Negri	2005	★★★	★★	★★	7
Beebe-Dimmer	2006	★★	★★	★★	6
Suzuki	2007	★★	★★	★★	6
Chen	2008	★★	★★	★★★	7
Mori	2011	★★★	★★	★★	7
Frank	2017	★★★	★★	★★★	8
Barber	2018	★★★	★★	★★★	8
Lamy	2018	★★★	★★	★★★	8