Table 3.

Quality assessment of included studies: Newcastle–Ottawa Scale.

Cohort	Selection	Comparability	Outcome	Total
Nygaard, E., Slinning, K., Moe, V., and Walhovd, K. B., 2016 [23]	3	2	2	7
Ornoy, A., Segal, J., Bar-Hamburger, R., and Greenbaum, C., 2001 [20]	2	0	1	3
Levine, T. A., and Woodward, L. J., 2017 [15]	4	0	3	7
Case Control	Selection	Comparability	Exposure	Total
Konijnenberg, C., and Melinder, A., 2015 [32]	2	2	1	5
Davis, D. D., and Templer, D. I.,1988 [21]	3	1	2	6
Sandtorv et al., 2018 [31]	2	2	0	4
Wahlsten and Sarman, 2013 [17]	2	0	0	2