Table 1. Characteristics of all included studies.

				Preeclampsia		Health control
Study, year	Country	Age (mean ± S.D.)	Study type	n	Cu: mean ± S.D. (μg/l)	n	Cu: mean ± S.D. (μg/l)	Sample type	Fasting status
Açikgoz et al., 2006	Turkey	24.90±2.50	Case–control	16	2697±867	20	2810±884	Serum	No
Ahsan et al., 2013	Bangladesh	26.05±5.41	Cross-sectional	44	1105±130	27	1040±130	Serum	No
Atamer et al., 2005	Turkey	27.00±3.89	Cross-sectional	32	2612±472	28	1458±396	Serum	Overnight fast
Bakacak et al., 2015	Turkey	29.20±3.56	Case–control	38	1995±263.58	40	1524.5±133.64	Serum	Overnight fast
Borella et al., 1990	Italy	34-37	Case–control	24	3365.7±1245.4	35	2622.1±575.25	Plasma	Yes
Farzin et al., 2012	Iran	27.43±3.91	Case–control	60	1182.8±169.2	60	1165.5±152.3	Serum	Yes
Fenzl et al., 2013	Croatia	31.20	Case–control	30	2204.15±532.35	37	2082.6±476.45	Serum	Overnight fast
Ilhan et al., 2002	Turkey	25.00	Case–control	21	1767.3±259.1	30	1581.5±278.6	Plasma	Overnight fast
Kolusari et al., 2008	Turkey	27.91±5.21	Case–control	47	26.5±7.6	48	20.8±4.6	Serum	Overnight fast
Rafeeinia et al., 2014	Iran	26.50±3.90	Case–control	50	2400±640	50	1300±340	Serum	Overnight fast
Sarwar et al., 2013	Bangladesh	25.46±0.85	Case–control	50	1980±100	58	2580±60	Serum	8 h fasting condition
Serdar et al., 2006	Turkey	25.00±2.30	Case–control	30	1880±480	30	1590±380	Serum	No