Table 1. Summary of counts, fetus-time at risk, and rates per 10,000 for variables stratified on spontaneous abortion (SAB) vs. other pregnancy outcomes for the Danish National Birth Cohort (1996–2002).
| Not SAB | SAB | ||||
| N | Fetus-days* | N | Fetus-days* | Rate of SAB/10,000 fetus-days | |
| Letigen use † | |||||
| None | 92,930 | 6,547,875 | 4,408 | 108,617 | 6.6 |
| Pre-conception only | 219 | 17,680 | 13 | 274 | 7.2 |
| Both pre-conception and early pregnancy | 270 | 21,311 | 17 | 346 | 7.8 |
| Early pregnancy only | 37 | 2,725 | 5 | 71 | 17.9 |
| Missing timing | 4 | 327 | 0 | 0 | |
| Gestational age at entry (completed weeks) | |||||
| 5–8 | 29,102 | 2,766,449 | 2,878 | 76,695 | 10.1 |
| 9–12 | 40,260 | 2,886,894 | 1,435 | 30,006 | 4.9 |
| 13–16 | 18,680 | 839,147 | 118 | 2,465 | 1.4 |
| 17–20 | 5,418 | 97,428 | 12 | 142 | 1.2 |
| Maternal age (years) | |||||
| 15–19 | 987 | 64,538 | 40 | 1,120 | 6.1 |
| 20–24 | 11,399 | 818,878 | 464 | 11,806 | 5.6 |
| 25–29 | 38,814 | 2,797,147 | 1,609 | 40,299 | 5.7 |
| 30–34 | 31,581 | 2,183,600 | 1,506 | 37,775 | 6.8 |
| 35–39 | 9,756 | 666,161 | 683 | 15,781 | 10.0 |
| 40–46 | 923 | 59,594 | 141 | 2,527 | 22.7 |
| Gravidity | |||||
| No prior pregnancy | 30,573 | 2,215,384 | 966 | 25,344 | 4.3 |
| ≥1 prior pregnancy | 57,061 | 3,988,842 | 2,171 | 55,864 | 5.4 |
| Missing | 5,826 | 385,692 | 1,306 | 28,100 | |
| Planned pregnancy | |||||
| Planned | 66,705 | 4,785,563 | 2,440 | 63,180 | 5.0 |
| Partially planned | 11,080 | 765,877 | 371 | 9,349 | 4.8 |
| Not planned | 9,859 | 654,187 | 328 | 8,757 | 4.9 |
| Missing | 5,816 | 384,291 | 1,304 | 28,022 | |
| Infertility treatment | |||||
| Yes | 5,700 | 386,549 | 167 | 4,581 | 4.3 |
| No | 81,923 | 5,817,343 | 2,972 | 76,705 | 5.0 |
| Missing | 5,837 | 386,026 | 1,304 | 28,022 | |
| Prepregnancy body mass index | |||||
| Underweight (<18.5) | 3,870 | 272,001 | 163 | 4,507 | 5.9 |
| Normal (18.5–24.9) | 58,493 | 4,138,880 | 2,076 | 52,949 | 5.0 |
| Overweight (25.0–29.9) | 16,707 | 1,182,334 | 613 | 15,805 | 5.1 |
| Obese (> = 30.0) | 7,160 | 510,755 | 255 | 7,114 | 4.9 |
| Missing | 7,230 | 485,948 | 1,336 | 28,933 | |
| Exercise (hours/week) | |||||
| None | 55,769 | 3,920,465 | 1,589 | 43,290 | 4.0 |
| >0 to <2 | 17,494 | 1,241,710 | 626 | 16,024 | 5.0 |
| > = 2 to <4 | 9,599 | 697,141 | 543 | 13,291 | 7.6 |
| > = 4 to <7 | 3,504 | 254,635 | 256 | 5,895 | 9.8 |
| > = 7 | 1,271 | 91,193 | 124 | 2,774 | 13.2 |
| Missing | 5,823 | 384,774 | 1,305 | 28,034 | |
| Smoked during pregnancy (cigarette equivalents/day § ) | |||||
| None | 67,521 | 4,781,746 | 2,342 | 60,576 | 4.8 |
| >0 to 10 | 14,741 | 1,046,138 | 569 | 14,975 | 5.4 |
| >10 | 5,373 | 376,952 | 224 | 5,656 | 5.9 |
| Missing | 5,825 | 385,082 | 1,308 | 28,101 | |
| Alcohol during pregnancy (drinks/week) | |||||
| No drinks | 48,727 | 3,507,924 | 1,560 | 41,792 | 4.4 |
| >0 to <4 | 37,112 | 2,578,283 | 1,427 | 36,548 | 5.5 |
| > = 4 | 1,823 | 120,506 | 152 | 2,946 | 12.3 |
| Missing | 5,798 | 383,205 | 1,304 | 28,022 | |
| Coffee (cups/day) | |||||
| None | 48,693 | 3,507,238 | 1,477 | 40,674 | 4.2 |
| >0 to <4 | 27,519 | 1,922,961 | 1,016 | 25,636 | 5.2 |
| 4 to <8 | 8,493 | 575,907 | 440 | 10,171 | 7.5 |
| > = 8 | 2,932 | 198,957 | 203 | 4,734 | 10.0 |
| Missing | 5,823 | 384,855 | 1,307 | 28,093 | |
| Tea (cups/day) | |||||
| None | 32,583 | 2,311,375 | 1,200 | 31,184 | 5.1 |
| >0 to <4 | 39,427 | 2,793,264 | 1,334 | 34,381 | 4.7 |
| 4 to <8 | 11,928 | 842,605 | 428 | 11,156 | 5.0 |
| > = 8 | 3,699 | 257,799 | 176 | 4,534 | 6.7 |
| Missing | 5,823 | 384,875 | 1,305 | 28,053 | |
| Cola (liters/week) | |||||
| None | 29,967 | 2,125,366 | 1,136 | 30,021 | 5.3 |
| >0 to <1 | 42,896 | 3,026,527 | 1,310 | 33,935 | 4.3 |
| > = 1 | 14,758 | 1,051,921 | 689 | 17,210 | 6.4 |
| Missing | 5,839 | 386,104 | 1,308 | 28,142 | |
*
Observed fetus days at risk (i.e. time from entry to outcome, censoring, or end of risk period).
†
Pre-conception includes the 4 weeks prior to last menstrual period through gestational age 2 completed weeks, early pregnancy includes gestational age 3–13 completed weeks, missing time includes Letigen use during an undefined time.
§
1 cigarette = 1 cigarette equivalent, 1 cherrot = 2 cigarettes equivalents, 1 cigar = 2 cigarette equivalents, 1 pipe = 1.5 cigarette equivalents.