Table 2.

Associations of folate acid supplementation and dietary folate intake with the risk of LBW.

Folic acid/folate intake duration	NBW (n = 8581)	LBW (n = 650)
		Cases	ORa (95% CI)	ORa(95% CI)
Folic acid supplement
Non-users	1859	239	1.00	1.00
Users	6722	411	0.48 (0.40~0.56)	0.80 (0.66~0.97)
≤ 12 weeks	3500	262	0.58 (0.48~0.70)	0.84 (0.68~1.03)
>12 weeks	3222	149	0.60 (0.54~0.67)	0.71 (0.55~0.92)
P for trend			<0.001	<0.001
Before conception and during pregnancy	2542	129	0.40 (0.32~0.49)	0.78 (0.59~1.03)
<24 weeks	1179	75	0.50 (0.38~0.64)	0.85 (0.62~1.17)
≥24 weeks	1363	54	0.56 (0.48~0.65)	0.64 (0.44~0.93)
P for trend			<0.001	<0.001
Before conception only	326	19	0.45 (0.28~0.73)	0.71 (0.43~1.18)
≤ 8 weeks	138	10	0.56 (0.29~1.09)	0.73 (0.37~1.45)
>8 weeks	188	9	0.61 (0.43~0.86)	0.69 (0.34~1.41)
P for trend			0.002	0.031
During pregnancy only	3854	263	0.53 (0.44~0.64)	0.80 (0.65~0.99)
<12 weeks	1656	138	0.65 (0.52~0.81)	0.84 (0.66~1.07)
≥12 weeks	2198	125	0.67 (0.59~0.74)	0.72 (0.56~0.93)
P for trend			<0.001	<0.001
Dietary folate intake (μg/day)
Before pregnancy
Q1 <116.01	2090	218	1.00	1.00
Q2 116.01–158.54	2186	126	0.55 (0.44~0.69)	0.70 (0.54~1.00)
Q3 158.54–220.88	2134	168	0.87 (0.78~0.97)	1.02 (0.91~1.16)
Q4 ≥220.88	2171	138	0.85 (0.79~0.91)	0.96 (0.86~1.06)
P for trend			<0.001	0.255
During pregnancy
Q1 <149.81	2086	224	1.00	1.00
Q2 149.81–197.59	2125	151	0.66 (0.53~0.82)	1.01 (0.79~1.29)
Q3 197.59–263.67	2144	138	0.77 (0.69~0.86)	0.96 (0.84~1.10)
Q4 ≥263.67	2226	137	0.83 (0.77~0.90)	1.02 (0.91~1.15)
P for trend			<0.001	0.133

Odds ration (OR)^a univariate analyses.

^ORbadjusted for maternal age, monthly income per capita, maternal education level, smoking, maternal employ, weight gain during pregnancy, preeclampsia, cesarean section, parity, total energy intake, dietary folate intake, or folic acid supplement.