Table 3 Duration of folic acid and iron supplementation and risk of low birthweight using the information from maternal interview
CasesControlsCrude OR (95% CI)Adjusted OR* (95% CI)
Folic acid (days)
    ⩽60902521.05 (0.77 to 1.43)0.98 (0.72 to 1.34)
    61–120411041.16 (0.76 to 1.76)1.01 (0.66 to 1.54)
    >15017660.76 (0.41 to 1.35)0.79 (0.44 to 1.42)
    p for trend0.5690.474
Iron (days)
    ⩽60851411.04 (0.64 to 1.72)0.96 (0.58 to 1.59)
    61–120952650.62 (0.39 to 1.00)0.54 (0.34 to 0.88)
    >120994500.38 (0.24 to 0.61)0.35 (0.22 to 0.56)
    p for trend<0.001<0.001
  • 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.