Table 1 General parameters of total participated couples and case-controlled couples
Total couples | Case-controlled couples (1:4) | Case-controlled couples (1:10) | |||||||
|---|---|---|---|---|---|---|---|---|---|
No birth defects | Birth defects | P value | No birth defects | Birth defects | P value | No birth defects | Birth defects | P value | |
(N = 566,948) | (N = 599) | (N = 2396) | (N = 599) | (N = 5990) | (N = 599) | ||||
Maternal age (years) | 0.094 | 0.706 | 0.833 | ||||||
20–24 | 139,837 (24.66) | 142 (23.71) | 540 (22.54) | 142 (23.71) | 1354 (22.60) | 142 (23.71) | |||
25–29 | 282,041 (49.75) | 300 (50.08) | 1170 (48.83) | 300 (50.08) | 2930 (48.91) | 300 (50.08) | |||
30–34 | 107,784 (19.01) | 101 (16.86) | 528 (22.04) | 101 (16.86) | 1307 (21.82) | 101 (16.86) | |||
35–39 | 28,824 (5.08) | 46 (7.68) | 131 (5.47) | 46 (7.68) | 310 (5.18) | 46 (7.68) | |||
≥ 40 | 8462 (1.49) | 10 (1.67) | 27 (1.13) | 10 (1.67) | 89 (1.49) | 10 (1.67) | |||
Paternal age (years) | 0.101 | 0.962 | 0.993 | ||||||
20–24 | 44,522 (7.85) | 50 (8.35) | 166 (6.93) | 50 (8.35) | 392 (6.54) | 50 (8.35) | |||
25–29 | 283,375 (49.98) | 276 (46.08) | 1151 (48.04) | 276 (46.08) | 2892 (48.28) | 276 (46.08) | |||
30–34 | 161,582 (28.50) | 179 (29.88) | 711 (29.67) | 179 (29.88) | 1794 (29.95) | 179 (29.88) | |||
35–39 | 56,112 (9.90) | 66 (11.02) | 274 (11.44) | 66 (11.02) | 663 (11.07) | 66 (11.02) | |||
≥ 40 | 21,357 (3.77) | 28 (4.67) | 94 (3.92) | 28 (4.67) | 249 (4.16) | 28 (4.67) | |||
Maternal education | / | / | |||||||
Illiteracy | 1178 (0.21) | 1 (0.17) | 1.000 | 8 (0.33) | 1 (0.17) | 0.698 | 20 (0.33) | 1 (0.17) | 0.716 |
Primary school | 24,503 (4.32) | 32 (5.34) | 0.226 | 127 (5.30) | 32 (5.34) | 1.000 | 318 (5.31) | 32 (5.34) | 0.924 |
Secondary school | 368,259 (64.95) | 390 (65.11) | 0.966 | 1555 (64.90) | 390 (65.11) | 0.962 | 3893 (64.99) | 390 (65.11) | 0.964 |
High school | 113,230 (19.97) | 106 (17.70) | 0.168 | 418 (17.45) | 106 (17.70) | 0.904 | 1043 (17.41) | 106 (17.70) | 0.865 |
College or undergraduate | 58,952 (10.40) | 70 (11.69) | 0.315 | 283 (11.81) | 70 (11.69) | 1.000 | 701 (11.70) | 70 (11.69) | 1.000 |
Postgraduate or above | 826 (0.15) | 0 (0.00) | 1.000 | 5 (0.21) | 0 (0.00) | 0.590 | 15 (0.25) | 0 (0.00) | 0.389 |
Paternal education | / | / | / | ||||||
Illiteracy | 558 (0.10) | 1 (0.17) | 0.446 | 8 (0.33) | 1 (0.17) | 0.698 | 14 (0.23) | 1 (0.17) | 1.000 |
Primary school | 21,330 (3.76) | 28 (4.67) | 0.236 | 125 (5.22) | 28 (4.67) | 0.678 | 281 (4.69) | 28 (4.67) | 1.000 |
Secondary school | 356,604 (62.90) | 383 (63.94) | 0.612 | 1495 (62.40) | 383 (63.94) | 0.509 | 3761 (62.79) | 383 (63.94) | 0.595 |
High school | 122,920 (21.68) | 109 (18.20) | 0.042 | 465 (19.41) | 109 (18.20) | 0.524 | 1179 (19.68) | 109 (18.20) | 0.418 |
College or undergraduate | 64,271 (11.34) | 77 (12.85) | 0.246 | 298 (12.44) | 77 (12.85) | 0.783 | 741 (12.37) | 77 (12.85) | 0.745 |
Postgraduate or above | 1265 (0.22) | 1 (0.17) | 1.000 | 5 (0.21) | 1 (0.17) | 1.000 | 14 (0.23) | 1 (0.17) | 1.000 |
Maternal occupation | / | / | / | ||||||
Farmers | 432,297 (76.25) | 444 (74.12) | 0.230 | 1765 (73.66) | 444 (74.12) | 0.836 | 4444 (74.19) | 444 (74.12) | 0.961 |
Workers | 56,391 (9.95) | 54 (9.02) | 0.494 | 242 (10.10) | 54 (9.02) | 0.445 | 615 (10.27) | 54 (9.02) | 0.357 |
Service officer | 22,107 (3.90) | 24 (4.01) | 0.833 | 102 (4.26) | 24 (4.01) | 0.909 | 226 (3.77) | 24 (4.01) | 0.737 |
Business | 11,154 (1.97) | 13 (2.17) | 0.658 | 46 (1.92) | 13 (2.17) | 0.742 | 108 (1.80) | 13 (2.17) | 0.522 |
Housewife | 12,188 (2.15) | 16 (2.67) | 0.395 | 60 (2.50) | 16 (2.67) | 0.773 | 139 (2.32) | 16 (2.67) | 0.571 |
Teachers/officials | 21,487 (3.79) | 31 (5.18) | 0.085 | 121 (5.05) | 31 (5.18) | 0.917 | 304 (5.08) | 31 (5.18) | 0.922 |
Others | 11,324 (2.00) | 17 (2.84) | 0.142 | 60 (2.50) | 17 (2.84) | 0.665 | 154 (2.57) | 17 (2.84) | 0.685 |
Paternal occupation | / | / | / | ||||||
Farmers | 420,794 (74.22) | 425 (70.95) | 0.068 | 1719 (71.74) | 425 (70.95) | 0.723 | 4325 (72.2) | 425 (70.95) | 0.535 |
Workers | 71,968 (12.69) | 77 (12.85) | 0.902 | 312 (13.02) | 77 (12.85) | 0.946 | 772 (12.89) | 77 (12.85) | 1.000 |
Service officer | 19,821 (3.50) | 19 (3.17) | 0.823 | 97 (4.05) | 19 (3.17) | 0.346 | 217 (3.62) | 19 (3.17) | 0.645 |
Business | 19,509 (3.44) | 22 (3.67) | 0.736 | 87 (3.63) | 22 (3.67) | 1.000 | 212 (3.54) | 22 (3.67) | 0.817 |
Househusband | 778 (0.14) | 0 (0.00) | 1.000 | 6 (0.25) | 0 (0.00) | 0.606 | 13 (0.22) | 0 (0.00) | 0.623 |
Teachers/officials | 20,316 (3.58) | 35 (5.84) | 0.006 | 98 (4.09) | 35 (5.84) | 0.075 | 259 (4.32) | 35 (5.84) | 0.096 |
Others | 13,762 (2.43) | 21 (3.51) | 0.108 | 77 (3.21) | 21 (3.51) | 0.701 | 192 (3.21) | 21 (3.51) | 0.716 |
Maternal residence status | 0.931 | 0.522 | 0.665 | ||||||
Rural | 533,260 (94.06) | 563 (93.99) | 2232 (93.16) | 563 (93.99) | 5594 (93.39) | 563 (93.99) | |||
Urban | 33,688 (5.94) | 36 (6.01) | 164 (6.84) | 36 (6.01) | 396 (6.61) | 36 (6.01) | |||
Paternal residence status | 0.180 | 1.000 | 1.000 | ||||||
Rural | 525,830 (92.75) | 547 (91.32) | 2186 (91.24) | 547 (91.32) | 5471 (91.34) | 547 (91.32) | |||
Urban | 41,118 (7.25) | 52 (8.68) | 210 (8.76) | 52 (8.68) | 519 (8.66) | 52 (8.68) | |||
Maternal adverse pregnancy history | 6.46e-5 | 0.469 | 0.631 | ||||||
Yes | 15,244 (2.69) | 34 (5.68) | 119 (4.97) | 34 (5.68) | 312 (5.21) | 34 (5.68) | |||
No | 551,704 (97.31) | 565 (94.32) | 2277 (95.03) | 565 (94.32) | 5678 (94.79) | 565 (94.32) | |||
Wives with birth defects | 0.001 | 1.000 | 1.000 | ||||||
Yes | 1070 (0.19) | 6 (1.00) | 27 (1.13) | 6 (1.00) | 69 (1.15) | 6 (1.00) | |||
No | 565,878 (99.81) | 593 (99.00) | 2369 (98.87) | 593 (99.00) | 5921 (98.85) | 593 (99.00) | |||
Maternal passive smoking | / | / | / | ||||||
No | 474,858 (83.76) | 461 (76.96) | 1.83e-5 | 1833 (76.5) | 461 (76.96) | 0.829 | 4575 (76.38) | 461 (76.96) | 0.801 |
Occasionally | 81,755 (14.42) | 117 (19.53) | 5.85e-4 | 482 (20.12) | 117 (19.53) | 0.775 | 1199 (20.02) | 117 (19.53) | 0.830 |
Often | 10,335 (1.82) | 21 (3.51) | 0.005 | 81 (3.38) | 21 (3.51) | 0.900 | 216 (3.61) | 21 (3.51) | 1.000 |
Maternal exposed to toxic substances | 5.96e-4 | 0.467 | 1.000 | ||||||
Yes | 36,581 (6.45) | 61 (10.18) | 272 (11.35) | 61 (10.18) | 616 (10.28) | 61 (10.18) | |||
No | 530,367 (93.55) | 538 (89.82) | 2124 (88.65) | 538 (89.82) | 5374 (89.72) | 538 (89.82) | |||
Maternal exposed to noise | 5.76e-4 | 1.000 | 1.000 | ||||||
Yes | 6952 (1.23) | 18 (3.01) | 74 (3.09) | 18 (3.01) | 188 (3.14) | 18 (3.01) | |||
No | 559,996 (98.77) | 581 (96.99) | 2322 (96.91) | 581 (96.99) | 5802 (96.86) | 581 (96.99) | |||
Maternal exposure to cats and dogs | 1.63e-4 | 0.640 | 0.745 | ||||||
Yes | 10,964 (1.93) | 26 (4.34) | 93 (3.88) | 26 (4.34) | 244 (4.07) | 26 (4.34) | |||
No | 555,984 (98.07) | 573 (95.66) | 2303 (96.12) | 573 (95.66) | 5746 (95.93) | 573 (95.66) | |||
Paternal smoking | 3.04e-5 | 0.888 | 0.860 | ||||||
Yes | 167,938 (29.62) | 225 (37.56) | 908 (37.90) | 225 (37.56) | 2275 (37.98) | 225 (37.56) | |||
No | 399,010 (70.38) | 374 (62.44) | 1488 (62.10) | 374 (62.44) | 3715 (62.02) | 374 (62.44) | |||
Paternal passive smoking | / | / | / | ||||||
No | 401,575 (70.83) | 375 (62.6) | 1.51e-5 | 1487 (62.06) | 375 (62.6) | 0.814 | 3711 (61.95) | 375 (62.6) | 0.791 |
Occasionally | 148,097 (26.12) | 192 (32.05) | 0.001 | 781 (32.6) | 192 (32.05) | 0.845 | 1926 (32.15) | 192 (32.05) | 1.000 |
Often | 17,276 (3.05) | 32 (5.34) | 0.003 | 128 (5.34) | 32 (5.34) | 1.000 | 353 (5.89) | 32 (5.34) | 0.648 |
Paternal alcohol consumption | / | / | / | ||||||
No | 392,995 (69.32) | 356 (59.43) | 3.14e-7 | 1439 (60.06) | 356 (59.43) | 0.780 | 3549 (59.25) | 356 (59.43) | 0.965 |
Occasionally | 166,814 (29.42) | 233 (38.90) | 7.38e-7 | 918 (38.31) | 233 (38.9) | 0.814 | 2340 (39.07) | 233 (38.9) | 0.965 |
Often | 7139 (1.26) | 10 (1.67) | 0.355 | 39 (1.63) | 10 (1.67) | 1.0 | 101 (1.69) | 10 (1.67) | 1.0 |
Paternal exposed to toxic substances | 5.0e-7 | 0.734 | 0.900 | ||||||
Yes | 42,266 (7.46) | 80 (13.36) | 308 (12.85) | 80 (13.36) | 789 (13.17) | 80 (13.36) | |||
No | 524,682 (92.54) | 519 (86.64) | 2088 (87.15) | 519 (86.64) | 5201 (86.83) | 519 (86.64) | |||
Maternal folic acid supplementation | 0.145 | 0.039 | 0.024 | ||||||
Taking | 423,737 (74.74) | 432 (72.12) | 1827 (76.25) | 432 (72.12) | 4573 (76.34) | 432 (72.12) | |||
No taking | 143,211 (25.26) | 167 (27.88) | 569 (23.75) | 167 (27.88) | 1417 (23.66) | 167 (27.88) | |||
Folic acid timing | |||||||||
≥ 3 months before conception | 212,740 (37.52) | 163 (27.21) | 1.18e-7 | 852 (35.56) | 163 (27.21) | 1.11e-4 | 2116 (35.33) | 163 (27.21) | 5.92e-5 |
< 3 months before conception | 83,765 (14.77) | 97 (16.19) | 0.327 | 426 (17.78) | 97 (16.19) | 0.400 | 1066 (17.8) | 97 (16.19) | 0.400 |
After conception | 127,232 (22.44) | 172 (28.71) | 3.40e-4 | 549 (22.91) | 172 (28.71) | 0.003 | 1391 (23.22) | 172 (28.71) | 0.003 |
No taking | 143,211 (25.26) | 167 (27.88) | 0.145 | 569 (23.75) | 167 (27.88) | 0.039 | 1417 (23.66) | 167 (27.88) | 0.024 |