Table 1.

Normal homocysteine (Hct) levels reported in the literature.

Authors	Population	Number of normal subjects	Hct levels (μmol/L)
			First trimester	Second trimester	Third trimester
Walker et al. [15]	Canadian	155	5.6 ± 1.6 (8-16 w)	4.3 ± 1.0 (20-28 w)	5.6 ± 2.3 (32-42 w)
Hogg et al. [16]	Italian	63	—	4.7 ± 1.4 (26 w)	5.3 ± 1.8 (37 w)
Bondevik et al. [17]	Nepalese	382	9.9 (9.1-10.6)	9.3 (8.6-10.1)	9.4 (8.5-10.3)
Murphy et al. [18]	Spanish	54	6.48 ± 1.30 (8 w)	5.22 ± 1.29 (20 w)	5.16 ± 1.32 (32 w)
Cotter et al. [19]	Irish	142	7.07 ± 1.5	—	—
Velzing-Aarts et al. [20]	West African	50	9.42 (95% RI: 5.50-16.12) (9 w)	7.28 (95% RI: 4.28-12.40) (16 w)	6.89 (95% RI: 3.93-12.06) (28 w)
				7.33 (95% RI: 4.25-12.64) (20 w)	7.17 (95% RI: 4.38-11.73) (32 w)
				7.11 (95% RI: 4.03-12.55) (24 w)	7.60 (95% RI: 4.46-12.96) (36 w)
Milman et al. [21]	Danish	406	—	6.4 (3.6-9.4) (18 w)	7.0 (4.0-9.7) (32 w)
					7.7 (5.2-12.0) (39 w)
					10.8 (6.8-19.3) (8 w after delivery)
Milman et al. [22]	Danish	434	—	6.06 (3.34-11.00) (18 w)	6.61 (3.93-11.10) (32 w)
					7.78 (4.72-12.81) (39 w)
					10.99 (5.85-20.64) (8 w after delivery)
Wallace et al. [23]	Seychelles	226	5.83 (4.03-10.38)	6.84 (4.33-12.93) (28 w)	12.4 (5.91-23.17) (delivery)
Hay et al. [24]	Nordic	364	—	4.7 (4.5-4.9) (17-19 w)	—
Hogeveen et al. [25]	Dutch	366	—	5.5 (4.5-6.7) (30-34 w)	—
Samuel et al. [26]	South Indian	360	9.22 (5.74-15.08)	—	—
Choi et al. [27]	Korean	278	10.6 (8.9-15.7) (5-13 w)	10.6 (8.2-13.9) (14-26 w)	10.2 (7.9-14.0) (27-40 w)
Maged et al. [28]	Egyptian	453	—	4.70 ± 2.08 (15-19 w)	—
Yang et al. [29]	Chinese	354	5.79-11.86	5.79-11.86	6.13-16.75

RI: reference interval.