Table 1 Background characteristics of participants by mode of conception
Natural conception | OI without ART | Conventional IVF-ET | ICSI | |||||
|---|---|---|---|---|---|---|---|---|
N = 90,506 | N = 3939 | N = 1476 | N = 1671 | |||||
Median | IQR | Median | IQR | Median | IQR | Median | IQR | |
Maternal age (years) | 31 | 8 | 33 | 6 | 36 | 6 | 36 | 6 |
Missing (N) | 733 | 31 | 4 | 17 | ||||
Maternal height (cm) | 158.0 | 8.0 | 158.0 | 7.5 | 158.7 | 8.0 | 158.5 | 7.0 |
Missing (N) | 477 | 23 | 3 | 6 | ||||
Maternal BMI before pregnancy (kg/m2) | 20.6 | 3.5 | 20.6 | 3.7 | 20.7 | 3.4 | 20.7 | 3.3 |
Missing (N) | 1089 | 41 | 15 | 17 | ||||
Maternal weight before delivery (kg) | 62.3 | 10.6 | 62.1 | 11.1 | 62.4 | 10.6 | 61.8 | 10.5 |
Missing (N) | 3019 | 158 | 55 | 79 | ||||
N | % | N | % | N | % | N | % | |
Parity | ||||||||
0 | 33,760 | 38.2 | 2290 | 59.9 | 949 | 66.0 | 1089 | 68.1 |
1 | 34,934 | 39.5 | 1331 | 34.8 | 447 | 31.1 | 469 | 29.3 |
2 or more | 19,712 | 22.3 | 201 | 5.3 | 42 | 2.9 | 42 | 2.6 |
(Missing) | 2100 | 117 | 38 | 71 | ||||
Prior cesarean section | ||||||||
No | 82,242 | 90.9 | 3680 | 93.5 | 1346 | 91.2 | 1530 | 91.6 |
Yes | 8200 | 9.1 | 257 | 6.5 | 130 | 8.8 | 141 | 8.4 |
(Missing) | 64 | 2 | 0 | 0 | ||||
Marital status | ||||||||
Married | 85,789 | 95.2 | 3919 | 99.6 | 1474 | 100.0 | 1668 | 99.8 |
Single | 4304 | 4.8 | 16 | 0.4 | 0 | 0.0 | 3 | 0.2 |
(Missing) | 413 | 4 | 2 | 0 | ||||
Pre-existing maternal condition | ||||||||
No | 74,963 | 85.4 | 3080 | 81.3 | 1087 | 75.3 | 1242 | 77.6 |
Yes | 12,858 | 14.6 | 710 | 18.7 | 357 | 24.7 | 359 | 22.4 |
(Missing) | 245 | 4 | 1 | 3 | ||||
Folic acid supplementation | ||||||||
No | 47,803 | 53.0 | 1310 | 33.3 | 470 | 31.9 | 476 | 28.5 |
A few times per month | 4610 | 5.1 | 184 | 4.7 | 38 | 2.6 | 52 | 3.1 |
A few times per week | 14,127 | 15.7 | 735 | 18.7 | 251 | 17.0 | 293 | 17.6 |
Daily | 23,721 | 26.3 | 1706 | 43.4 | 716 | 48.5 | 847 | 50.8 |
(Missing) | 695 | 21 | 8 | 7 | ||||
Maternal smoking during pregnancy | ||||||||
No | 85,152 | 94.8 | 3867 | 98.7 | 1453 | 99.0 | 1649 | 99.1 |
Yes | 4659 | 5.2 | 51 | 1.3 | 15 | 1.0 | 15 | 0.9 |
(Missing) | 440 | 10 | 3 | 3 | ||||
Maternal drinking during pregnancy | ||||||||
No | 81,033 | 90.0 | 3579 | 91.1 | 1362 | 92.5 | 1525 | 91.4 |
Yes | 9033 | 10.0 | 350 | 8.9 | 111 | 7.5 | 143 | 8.6 |
(Missing) | 2512 | 100 | 38 | 42 | ||||
Maternal educational level | ||||||||
Junior high/high school | 33,026 | 37.5 | 904 | 23.5 | 335 | 23.3 | 358 | 22.0 |
Vocational school/junior college | 36,499 | 41.5 | 1866 | 48.6 | 673 | 46.8 | 777 | 47.7 |
University/graduate school | 18,469 | 21.0 | 1069 | 27.8 | 430 | 29.9 | 494 | 30.3 |
(Missing) | 1902 | 47 | 15 | 23 | ||||
Paternal smoking | ||||||||
No | 45,916 | 51.8 | 2464 | 63.3 | 977 | 66.9 | 1145 | 69.5 |
Yes | 42,688 | 48.2 | 1428 | 36.7 | 484 | 33.1 | 503 | 30.5 |
(Missing) | 3105 | 105 | 39 | 45 | ||||
Paternal educational level | ||||||||
Junior high/high school | 39,601 | 45.3 | 1229 | 32.1 | 475 | 33.1 | 503 | 30.9 |
Vocational school/junior college | 19,687 | 22.5 | 902 | 23.5 | 272 | 18.9 | 351 | 21.6 |
University/graduate school | 28,113 | 32.2 | 1703 | 44.4 | 690 | 48.0 | 772 | 47.5 |
(Missing) | 8435 | 283 | 93 | 116 | ||||
Household income (×10,000 Japanese yen) | ||||||||
< 200 | 4956 | 6.0 | 73 | 2.0 | 17 | 1.2 | 20 | 1.3 |
≥ 200, < 400 | 29,346 | 35.8 | 949 | 26.0 | 279 | 20.2 | 258 | 16.6 |
≥ 400, < 600 | 26,979 | 32.9 | 1319 | 36.1 | 480 | 34.7 | 521 | 33.5 |
≥ 600, < 800 | 12,554 | 15.3 | 747 | 20.4 | 318 | 23.0 | 391 | 25.1 |
≥ 800, < 1000 | 5012 | 6.1 | 328 | 9.0 | 161 | 11.6 | 204 | 13.1 |
≥ 1000 | 3224 | 3.9 | 240 | 6.6 | 128 | 9.3 | 161 | 10.4 |
(Missing) | 8435 | 283 | 93 | 116 | ||||