Table 1 Crude odds ratios for anencephaly according to some maternal characteristics.
| Variable | Cases (n = 151) | Controls (n = 151) | OR | (95% CI) | ||
|---|---|---|---|---|---|---|
| n | % | n | % | |||
| Age | ||||||
| <18 years | 10 | 6.62 | 16 | 10.60 | 1 | |
| 18–34 years | 124 | 82.12 | 126 | 83.44 | 1.61 | 0.66–3.87 |
| 35–44 years | 17 | 11.26 | 9 | 5.96 | 3.24 | 0.99–10.65 |
| Educational level (years of school) | ||||||
| High school and greater (⩾12) | 9 | 6.00 | 22 | 14.97 | 1 | |
| Secondary and preparatory incomplete (9–11) | 23 | 15.33 | 37 | 25.17 | 1.69 | 0.59–4.80 |
| Primary and secondary incomplete (6–8) | 47 | 31.33 | 46 | 31.29 | 3.46 | 1.25–9.53 |
| No education/primary incomplete (<6) | 71 | 47.33 | 42 | 28.57 | 5.92 | 2.09–16.72 |
| Income level (US$1 = 10 pesos) | ||||||
| >2500 pesos a month | 16 | 10.96 | 22 | 14.86 | 1 | |
| 1000–2500 pesos a month | 55 | 37.67 | 75 | 50.68 | 1.27 | 0.51–3.15 |
| <1000 pesos a month | 75 | 51.37 | 51 | 34.46 | 2.95 | 1.29–7.74 |
| Familial reproductive history | ||||||
| Reproductive problems* | 14 | 8.92 | 9 | 5.96 | 1.62 | 0.67–3.92 |
| Congenital malformations | 9 | 5.73 | 2 | 1.32 | 4.50 | 0.97–20.83 |
| Number of pregnancies | ||||||
| 1–2 | 78 | 51.66 | 109 | 72.19 | 1 | |
| 3–4 | 39 | 25.83 | 27 | 17.88 | 1.93 | 1.07–3.49 |
| >4 | 34 | 22.52 | 15 | 9.93 | 3.84 | 1.72–8.59 |
| Fever in the ARP | 22 | 14.01 | 13 | 8.61 | 1.90 | 0.88–4.09 |
| Adverse reproductive antecedents with previous children† | ||||||
| Multiparous without antecedents | 52 | 35.14 | 55 | 38.19 | 1 | |
| Multiparous with antecedents | 46 | 31.08 | 20 | 13.89 | 2.12 | 1.12–4.02 |
| Primiparous | 50 | 33.78 | 69 | 47.92 | 0.71 | 0.40–1.27 |
| Lifetime alcohol use | 50 | 32.48 | 62 | 41.61 | 0.59 | 0.34–1.05 |
| Use of alcohol at the beginning of pregnancy | 13 | 25.49 | 15 | 25.00 | 1.00 | 0.20–4.95 |
| Lifetime use of tobacco | 23 | 14.65 | 32 | 21.33 | 0.59 | 0.30–1.17 |
| Use of tobacco at the beginning of pregnancy | 6 | 26.09 | 9 | 28.13 | 0.66 | 0.24–1.87 |
| Use of wood to cook during the ARP | 87 | 57.62 | 60 | 39.74 | 3.25 | 1.70–6.21 |
| Exposure to domestic pesticides during the ARP | 37 | 24.50 | 35 | 23.18 | 1.08 | 0.63–1.86 |
| Exposure to domestic solvents during the ARP | 11 | 7.69 | 12 | 7.95 | 0.92 | 0.40–2.08 |
| Occupation in the ARP‡ | ||||||
| Professionals | 5 | 3.31 | 9 | 5.96 | 0.5 | 0.15–1.66 |
| Industry | 14 | 9.93 | 11 | 8.09 | 1.43 | 0.54–3.75 |
| Agriculture | 13 | 10.08 | 8 | 6.02 | 3.67 | 1.02–13.14 |
| Services | 6 | 4.03 | 7 | 4.83 | 0.86 | 0.29–2.55 |
| Other occupations§ | 15 | 9.93 | 25 | 16.56 | 0.55 | 0.27–1.10 |
| Occupation in the NARP‡ | ||||||
| Professionals | 1 | 0.66 | 4 | 2.65 | 0.25 | 0.03–2.24 |
| Industry | 10 | 7.30 | 13 | 9.42 | 0.67 | 0.24–1.87 |
| Agriculture | 27 | 18.88 | 17 | 11.97 | 1.78 | 0.79–4.02 |
| Services | 2 | 1.38 | 6 | 4.17 | 0.33 | 0.07–1.65 |
| Other occupations§ | 11 | 7.28 | 14 | 9.27 | 0.75 | 0.32–1.78 |
| Folate intake | ||||||
| ⩾400 μg/day | 48 | 32.00 | 59 | 40.41 | 1 | |
| <400 μg/day | 102 | 68.00 | 87 | 59.59 | 1.58 | 0.94–2.63 |
*Includes problems with having children, repeated abortions, and infertility.
†Includes stillbirths, premature births, malformations, and abortions.
‡Reference level includes total women except the occupation considered in each case.
§Does not include women who are housewives or students.
ARP (acute risk period): three months before and one month after the last menstruation; NARP (non‐acute risk period): exposure prior to the ARP.