Table 6. Risk Of Acute Lymphoblastic Leukemia Associated With Maternal Vitamin And Folic Acid Supplementation Any Time Before Or During Pregnancy: Stratified Analyses In Subsets Of Childhood Leukemia International Consortium Studies.

	Vitamins (Any Time)						Folic Acid (Any Time)
	No. Studies	No. Exposed		OR	(95% CI)a	Test for Interaction	No. Studies	No. Exposed		OR	(95% CI)a	Test for Interaction
		Controls	Cases					Controls	Cases
Immunophenotype
Overallb	10	6125	3585	0.87	(0.80–0.94)		6	1661	1001	0.86	(0.76–0.97)
B-cell	10	6125	3222	0.87	(0.80–0.95)	P = 0.45c	6	1661	905	0.86	(0.75–0.97)	P = 0.59c
T-cell	9	5897	363	0.81	(0.65–0.99)		6	1661	96	0.84	(0.62–1.14)
Maternal consumption of alcohol (any time)
Overallb	12	5989	3742	0.83	(0.76–0.91)		8	2168	1232	0.80	(0.71–0.90)
No	12	3274	2133	0.79	(0.71–0.89)	P = 0.66d	8	1059	595	0.75	(0.64–0.90)	P = 0.14d
Yes	12	2715	1609	0.89	(0.78–1.01)		8	1109	637	0.87	(0.74–1.02)
Parental educatione
Overallb	12	6640	4336	0.85	(0.78–0.92)		8	2164	1228	0.80	(0.71–0.89)
None/Primary	12	873	447	0.72	(0.60–0.88)	P = 0.14d	8	352	132	0.47	(0.33–0.68)	P = 0.01d
Secondary	12	2649	1879	0.78	(0.68–0.88)		8	660	410	0.73	(0.59–0.90)
Tertiary	12	3118	2010	0.97	(0.86–1.09)		8	1152	686	0.96	(0.82–1.12)
Child born before/after fortification
Overallb	12	6679	4348	0.85	(0.78–0.92)		8	2172	1233	0.80	(0.71–0.89)
Before fortification	12	6046	3971	0.86	(0.79–0.93)	P = 0.15d	8	1892	1075	0.78	(0.69–0.89)	P = 0.96d
After fortification	12	633	377	0.66	(0.45–0.97)		8	280	158	0.84	(0.64–1.11)

^aAdjusted for age, sex, ethnicity, parental education, and study. Or for parental education is adjusted for age, sex, ethnicity, and study

^bOverall OR is given on the entire subset for which data are available for a specific stratified analysis

^cWoolf test

^dLog ratio test

^eParental education defined as the highest education level between the mother and father