Table 2 Odds ratios of total neural tube defects (NTDs) and two of their subtypes (anencephaly and spina bifida) associated with exposure index (EI) to coal combustion during cooking

cOR ^b (95% CI)

0

1.00

1.00

1.00

1

3.60 (2.11–6.15)

< 0.001

3.95 (2.26–6.9)

< 0.001

3.84 (2.53–5.83)

< 0.001

2

3.01 (1.89–4.81)

< 0.001

3.46 (2.13–5.62)

< 0.001

3.18 (2.23–4.55)

< 0.001

P_trend

< 0.001

< 0.001

< 0.001

aOR1 ^c (95% CI)

0

1.00

1.00

1.00

1

1.76 (0.87–3.56)

0.113

2.43 (1.23–4.78)

< 0.05

2.33 (1.40–3.89)

< 0.01

2

1.37 (0.75–2.51)

0.303

2.20 (1.23–3.94)

< 0.01

1.73 (1.11–2.69)

< 0.05

P_trend

0.270

< 0.01

< 0.01

aOR2 ^d (95% CI)

0

1.00

1.00

1.00

1

1.61 (0.78–3.32)

0.199

2.60 (1.14–5.94)

< 0.05

1.95 (1.12–3.39)

< 0.05

2

1.74 (0.83–3.65)

0.143

4.45 (1.98–9.99)

< 0.001

3.10 (1.80–5.36)

< 0.001

P_trend

< 0.05

< 0.001

< 0.001

aOR3 ^e (95% CI)

0

1.00

1.00

1.00

1

1.74 (0.89–3.41)

0.106

2.27 (1.18–4.39)

< 0.05

2.23 (1.37–3.63)

< 0.01

2

1.45 (0.8–2.64)

0.219

2.29 (1.29–4.06)

< 0.01

1.84 (1.19–2.84)

< 0.01

P_trend

< 0.05

< 0.01

< 0.001