Table 5 Multivariate logistic regression analysis of risk factors for birth defects (Forward, Wald, α = 0.05)
Variables | Adjusted OR (95%CI) | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
Overall birth defects | Congenital heart defects | Congenital metabolic disorders | Congenital limb defects | Congenital ear defects | Congenital kidney and urinary defects | Cleft lip and/or palate | Chromosomal abnormalities | Congenital digestive system defects | Congenital nervous system defects | |
Sex | Â | Not entered | Â | Â | Not entered | Â | Not entered | Not entered | Not entered | Not entered |
 Females | Reference |  | Reference | Reference |  | Reference |  |  |  |  |
 Males | 1.49(1.39–1.61) |  | 3.86(3.15–4.72) | 1.34(1.14–1.58) |  | 2.35(1.65–3.34) |  |  |  |  |
 Unknown | 50.82(7.01-368.28) |  | Counter overflow | Counter overflow |  | 1621.08(223.15-11776.22) |  |  |  |  |
Residence | Not entered | Not entered | Â | Not entered | Â | Not entered | Not entered | Not entered | Not entered | Not entered |
 Urban |  |  | Reference |  | Reference |  |  |  |  |  |
 Rural |  |  | 1.21(1.01–1.44) |  | 0.76(0.58-1.00) |  |  |  |  |  |
Number of births | Â | Â | Not entered | Not entered | Not entered | Â | Â | Not entered | Not entered | Not entered |
 Singleton | Reference | Reference |  |  |  | Reference | Reference |  |  |  |
 Multiple births | 1.44(1.18–1.76) | 2.09(1.55–2.82) |  |  |  | 2.14(1.05–4.37) | 2.85(1.32–6.15) |  |  |  |
Paternal age (years old) | Â | Â | Â | Â | Â | Not entered | Not entered | Not entered | Not entered | Â |
 25–29 | Reference | Reference | Reference | Reference | Reference |  |  |  |  | Reference |
 < 20 | 2.20(1.19–4.09) | 2.34(0.70–7.85) | Counter overflow | 3.27(1.10–9.71) | 4.45(0.52–38.22) |  |  |  |  | Counter overflow |
 20–24 | 1.66(1.42–1.94) | 1.64(1.24–2.17) | 1.56(1.11–2.21) | 1.61(1.14–2.29) | 2.13(1.17–3.89) |  |  |  |  | 2.14(0.93–4.92) |
 30–34 | 0.69(0.63–0.77) | 0.73(0.61–0.87) | 0.63(0.50–0.78) | 0.65(0.52–0.80) | 0.54(0.37–0.78) |  |  |  |  | 0.57(0.31–1.03) |
 >=35 | 0.66(0.57–0.75) | 0.65(0.51–0.83) | 0.72(0.54–0.96) | 0.50(0.37–0.67) | 0.62(0.39-1.00) |  |  |  |  | 0.27(0.12–0.64) |
Maternal age (years old) | Â | Â | Â | Â | Â | Not entered | Â | Not entered | Not entered | Not entered |
 25–29 | Reference | Reference | Reference | Reference | Reference |  | Reference |  |  |  |
 < 20 | 0.89(0.67–1.18) | 0.62(0.35–1.12) | 1.21(0.72–2.06) | 1.00(0.56–1.78) | 0.42(0.11–1.52) |  | 3.14(1.24–7.95) |  |  |  |
 20–24 | 0.86(0.77–0.96) | 0.94(0.77–1.14) | 0.74(0.58–0.96) | 0.80(0.62–1.03) | 0.57(0.35–0.91) |  | 1.44(0.87–2.37) |  |  |  |
 30–34 | 1.16(1.04–1.29) | 1.20(1.00-1.45) | 1.02(0.81–1.30) | 1.37(1.09–1.73) | 1.39(0.95–2.04) |  | 0.74(0.44–1.26) |  |  |  |
 >=35 | 1.56(1.33–1.81) | 1.51(1.14–1.99) | 1.38(0.99–1.92) | 1.98(1.41–2.78) | 1.82(1.06–3.10) |  | 1.48(0.84–2.64) |  |  |  |
Number of pregnancies (times) | Not entered | Not entered | Not entered | Not entered | Not entered | Not entered | Not entered | Â | Not entered | Â |
 1 |  |  |  |  |  |  |  | Reference |  | Reference |
 2 |  |  |  |  |  |  |  | 0.76(0.42–1.38) |  | 2.27(1.19–4.32) |
 3 |  |  |  |  |  |  |  | 1.11(0.54–2.27) |  | 2.13(0.91–4.99) |
 >=4 |  |  |  |  |  |  |  | 2.03(1.06–3.88) |  | 3.03(1.23–7.47) |
Parity (times) | Not entered | Not entered | Not entered | Not entered | Not entered | Not entered | Not entered | Not entered | Not entered | Not entered |
 1 |  |  |  |  |  |  |  |  |  |  |
 2 |  |  |  |  |  |  |  |  |  |  |
 >=3 |  |  |  |  |  |  |  |  |  |  |
Maternal household registration | Â | Â | Â | Â | Â | Not entered | Not entered | Not entered | Not entered | Not entered |
 Local | Reference | Reference | Reference | Reference | Reference |  |  |  |  |  |
 Non-local | 2.96(2.39–3.67) | 3.57(2.54–5.03) | 1.89(1.06–3.37) | 2.94(1.86–4.66) | 3.26(1.60–6.65) |  |  |  |  |  |