TABLE 2.
Count of neural tube defect (NTD)-affected pregnancies and NTDs prevalence by sex, geographical region and folic acid (FA) use status, and male to female prevalence ratio by NTD type in north and south China, 1993–1996
| NTD type | Count | Prevalence per 10,000 pregnancies | Count | Prevalence per 10,000 pregnancies | Male to female prevalence ratio and 95% confidence interval |
|---|---|---|---|---|---|
| North: FA nonusers | Male (N = 38,921) | Female (N = 34,466) | |||
| Anencephaly | 16 | 4.11 | 29 | 8.41 | 0.49 (0.27, 0.90) |
| Craniorachischisis | 13 | 3.34 | 44 | 12.77 | 0.26 (0.14, 0.49) |
| Iniencephaly | 1 | 0.26 | 7 | 2.03 | 0.13 (0.02, 1.03) |
| Encephalocele | 14 | 3.60 | 14 | 4.06 | 0.89 (0.42, 1.86) |
| Spina bifida | 58 | 14.90 | 72 | 20.89 | 0.71 (0.50, 1.01) |
| All NTDs | 102 | 26.21 | 166 | 48.16 | 0.54 (0.43, 0.70) |
| North: FA users | Male (N = 5,343) | Female (N = 4,804) | |||
| Anencephaly | 1 | 1.87 | 0 | 0.00 | — |
| Craniorachischisis | 0 | 0.00 | 0 | 0.00 | — |
| Iniencephaly | 0 | 0.00 | 0 | 0.00 | — |
| Encephalocele | 1 | 1.87 | 1 | 2.08 | 0.90 (0.06, 14.37) |
| Spina bifida | 3 | 5.61 | 1 | 2.08 | 2.70 (0.28, 25.93) |
| All NTDs | 5 | 9.36 | 2 | 4.16 | 2.25 (0.44, 11.59) |
| South: FA nonusers | Male (N = 226,841) | Female (N = 205,316) | |||
| Anencephaly | 64 | 2.82 | 55 | 2.68 | 1.05 (0.73, 1.51) |
| Craniorachischisis | 13 | 0.57 | 29 | 1.41 | 0.41 (0.21, 0.78) |
| Iniencephaly | 1 | 0.04 | 6 | 0.29 | 0.15 (0.02 1.25) |
| Encephalocele | 27 | 1.19 | 31 | 1.51 | 0.79 (0.47, 1.32) |
| Spina bifida | 33 | 1.45 | 70 | 3.41 | 0.43 (0.28, 0.65) |
| All NTDs | 138 | 6.08 | 191 | 9.30 | 0.65 (0.53, 0.81) |
| South: FA users | Male (N = 25,590) | Female (N = 24,376) | |||
| Anencephaly | 7 | 2.74 | 7 | 2.87 | 0.95 (0.33, 2.72) |
| Craniorachischisis | 0 | 0.00 | 0 | 0.00 | — |
| Iniencephaly | 0 | 0.00 | 0 | 0.00 | — |
| Encephalocele | 5 | 1.95 | 3 | 1.23 | 1.59 (0.38, 6.64) |
| Spina bifida | 1 | 0.39 | 5 | 2.05 | 0.19 (0.02, 1.63) |
| All NTDs | 13 | 5.08 | 15 | 6.15 | 0.83 (0.39, 1.74) |
Note: The prevalence for each type of NTD was calculated as the number of NTD-affected pregnancies divided by the total number of pregnancies with known birth outcomes which could be confirmed as either having or not having an NTD. Two thousand twenty-nine (0.3%) infants and fetuses with unknown sex and 170 (0.03%) with ambiguous sex were excluded from the analysis for sex difference. Women with incomplete exposure to folic acid were excluded from the table.