Table 2 Association between folic acid, iron supplementation and risk of low birthweight using two sources of information (prenatal care record and maternal interview)

	Cases	Controls	Crude OR (95% CI)	Adjusted OR* (95% CI)
From prenatal care record
No.	24	44	1 (ref.)	1 (ref.)
Folic acid only	11	16	1.26 (0.45 to 3.44)	1.31 (0.50 to 3.42)
Iron only	82	248	0.61 (0.34 to 1.11)	0.59 (0.33 to 1.07)
Folic acid plus iron	120	365	0.60 (0.34 to 1.08)	0.55 (0.31 to 0.96)
NA	85	261
From maternal interview
No.	27	54	1 (ref.)	1 (ref.)
Folic acid only	14	17	1.65 (0.64 to 4.16)	1.43 (0.59 to 3.47)
Iron only	145	452	0.64 (0.38 to 1.10)	0.58 (0.34 to 0.98)
Folic acid plus iron	134	407	0.66 (0.39 to 1.13)	0.56 (0.33 to 0.96)
NA	2	4

NA, Not available; OR, odds ratio.
Crude and multiple risk factor-adjusted for (logistic regression) analyses.
*Adjusted for smoking, maternal education, maternal age, Kessner index, body mass index, obstetric diseases during pregnancy, gestational age, and weight gain during pregnancy.